False Premises: "The DM should maximize player fun."

What. The. Actual. Fuck.

Someone just said that today. In a public forum. That the only job of the DM is to maximize player fun. This discussion was related to race/class restrictions in 2nd Edition AD&D - but I have to tell you, I've never seen a more stupid sentiment in my life and I decided it needed a blog post. The obvious response is obvious:

NO.

I mean this is such obvious bullshit that no one should say it and expect to be taken seriously as a functional adult. This is the kind of crap I expect from toddlers and anyone spewing this verbal vomit should be treated as such.

Now, being the generally nice chap that I am, I will explain once - and once only - why this is a load of crap. Afterwards, if you still want to hold on to this crap, I'd recommend therapy or maybe electroshock treatment.

First, let's step back and answer: "What is a role playing game?"

Premise of a Role Playing Game

A role playing game is a set of structured rules administrated by a single individual to provide guidance around the actions of the players. In terms of AD&D, and D&D in general, the single individual is referred to as the DM and is given maximum leeway in both interpreting the rules and managing the table - in that, whatever the DM says is what the rule at the table and that is "rules as written." This is often referred to as "Rule Zero."

The players have control over their own agency. What this means is that once the players are at the table, with characters created within the scope of the DM's campaign setting, the players have full control over how their characters will react and explore the world. This is why DMPCs and railroading are terrible - they remove player agency either by making them passive to the world (DMPC) or making their agency and choices meaningless.

The DM, of course, is responsible for creating that world: plots, maps, encounters, managing the reactions of the players, allocating resources, evaluating material/rules, and resolving unexpected or unplanned player actions. Essentially the bookkeeping and management. This usually takes up time before and after a game as well, so once the players are done, the lonely DM is still at the table determining the ramifications of the game and planning the next session.

Now, let's discuss maximization.

The Premise and Problem of Maximization

Maximization, or more properly, the utility maximization problem is a microeconomic theory regarding consumer decisions. Typically the question is asked in regards to purchasing: "How should I spend my money in order to maximize my utility?" Money and time are both finite resources that can be viewed under the scope of this utilization formula. For gaming, the utilization problem can be expressed as: "How should I spend my time in order to maximize my utility?" where utility is fun.

Now there is a whole crap ton of work done on utility maximization problems. It's fascinating stuff and I encourage you to delve into it, but the key point that I think needs to be emphasized for this post is this: Although the theoretical utility curve created by the consumer/player will indicate that a theoretical choice is best, that choice might not exist. This is the opposite case of bounded rationality (where the player is unwilling to put in the time or effort to determine their maximum utility and thus they chose a suboptimal experience or product), but the effect is the same - the consumer/player is left with suboptimal choices based on their theoretical - but nonexistent - maximum.

For our player who is searching for his theoretical maximum, two problems get in the way of maximizing their fun:

1. Demand Pressure: There are only so many DMs. Since demand for DMs is high, and supply of DMs is low, DMs have greater control over the market and can offer those products they wish to offer and not necessarily what the market demands.
    
2. Subjective Probability: Subjective probability is based on a person’s own personal reasoning and judgment. It is the probability that the outcome a person is expecting will actually occur. There are no formal calculations for subjective probability but instead it is based on a person’s own knowledge and feelings. For us, any two given players looking at a proposed game will subjectively come to different assessments of their ability to enjoy that game. As a result, the player base is fractured, there is no agreed upon standard for evaluating and assessing a "fun game" meaning that any efforts by the player to maximize utility will be frustrated first by not having the ability to internally quantify their utility, and second being a part of a large demand side of people in a similar situation.
   
   It's important to note here that the fact that fun is subjective and internal means that it is impossible for any DM to actually meet the maximum utility of all players. Each one will have a utility maximum that is different from the others, including the DM themselves.

By chasing the theoretical maximum, which won't exist in the market, the player fails to maximize their utility. They want to be in the RPG market, they have time to spend on the RPG market, but they burn that time chasing something which they can't have.

Now, a rational actor who examines the market place and finds that there is nothing in that market place that offers what they want can handle it one of three ways. Let's look at the them:

1. Create their own Service: The player will offer to DM, establishing the game they want to play and inviting other players to join.
    
2. Adjust their Expectations: The player will seek to join a game where the game play is as close to possible to the theoretical maximum.
    
3. Do not adjust: The player will either not join games and thus get zero utility, or will join games and attempt to force the games to their preference which results in no one gaining utility (due to stress and frustration at the board, leading to DM burn out and reducing the DM supply, thus making it more difficult for everyone else). 

An additional problem, which makes three above such an issue, is that we're all attempting to maximize our utility. If the DM's maximization is at odds with the player's maximization, then the laws of supply and demand come into play. Limited supply and high demand mean that the player who is at odds with the DM will never be able to play a game. If the player can't adjust, or act as a DM, then the player will enter into a situation where zero utility for anyone is possible. Rational players and DMs, faced with a player like that, will remove the player in order to maximize their own utility.

Back to Gaming

So what does this all mean for role playing games? Simple. Be respectful when you're at the table. When a DM outlines their world take notes. If you like it well enough, play it. If you hate it, but can carry on, do so - nothing stops the player from taking notes and saying to the DM: "Hey if you want to take a break at some point, I came up with an awesome idea..."

Your DM would probably appreciate it.

Expanding on Variant Humans

Under 2nd edition rules, human characters are not seen as viable if you remove class restrictions. It's right in the DMG. The sum total of human benefits can be summed up as:

• Fairly common (no mechanical benefit)
• Generally well liked (no mechanical benefit)
• Can dual class (poor version of multiclassing)
• Unlimited access to all classes (not Comcast/Verizon unlimited. TRUE unlimited access)
• Most magic items are going to be sized for them (or elves, and half elves)

So when you want to remove class restrictions on demihuman players, you run into objections that it isn't fair. Heck, the DMG even says it:

The DM can, if he chooses, make any class available to any race. This will certainly make your players happy. But before throwing the doors open, consider the consequences. If the only special advantage humans have is given to all the races, who will want to play a human? Humans would be the weakest race in your world. Why play a 20th-level human paladin when you could play a 20th-level elven paladin and have all the abilities of paladins and elves? - Page 21, DMG, Chapter 2 PC Races - A Nonhuman World

Now, ignoring for a moment player agency and also ignoring the world building consequences (that's an entirely different rant), it is true that, mechanically, humans get the short end of the stick. However, this can be adjusted without damaging the game balance or engaging in any more power creep then 2nd Edition engages in already! And the main reason has nothing to do with demihumans - though it helps with that.

There is a strong cultural variance between groups that live in radically different situations - even apparent in the Middle Ages. Look at perceptions of Appalachia versus the cities of coastal Virginia. And there are even further divisions based on the role that an individual has within a city or rural area: landed lords vs free peasants (i.e. the economic conditions that led to Enclosure), or the "town vs gown" debates, or what to do with peasant workers migrating en masse to cities. Guilds only took in so many people, and the huge labor force cause significant cultural changes.

At the same time, these cultural variations lead to skill variations. During enclosure, peasants kicked out of common lands lost the security and safety that the old system provided. They were unable to transition their existing skills into the new market, and this lead to revolts and riots during the transition period. In Ireland, food and land seizures that disrupted the population lead to the formation of the Irish Republican Brotherhood (later the IRA).

The primary point of all this is that there are significant differences between human populations in terms of skills, temperament and inclination. What unites them is a general view from other races that humans are dirty (high populations crammed into cities; or crammed into small villages and living with the mud and animals), but also diplomatic and generally well liked. Because of that I give all humans two racial abilities:

• Peacekeepers: Humans in general are more trusted then other races. Both elves and orcs, racial enemies turn to humans at times and though humans might have preferences (evil preferring orcs, good preferring elves), there is generally no way to know at first. As such, humans always start one level higher on encounter tables: Hostile to threatening, threatening to indifferent, indifferent to friendly. This is the case until the human does something to indicate that they should be treated differently.
• Disease Resistant: In most fantasy settings humans cities are often described in typical medieval fashion compared to elven or dwarven cities: dirty, squalid, and packed to the parapet. These conditions have one natural outcome: disease. Disease often rips through human cities and kills the weak. Those left multiply and grow, having stronger resistance. Humans thus gain resistance to non-magical disease similar to how halflings and dwarves have resistance to poison and magic. They gain a +1 to their saves for every 3.5 points of constitution. The save type depends on the special attack used by the creature. Rats, for example, use the Save vs. Poison chart. If no save is allowed or outlined (i.e. rabies from a large bat) the character can make a Save vs. Poison without their bonus.[/list]

In addition to the above, I recommend the following variants based on regional variance:

Rural

Peasants and nobility that live out of the cities on estates. Humans of this type tend to favor outdoor activities and are often seen as uncultured by their urban peers. Typically they live in small villages and hamlets and are engaged in agricultural work, logging, or mining. Rural humans get:

• Ability Score Adjustment: +1 to Constitution, -1 to Intelligence. Rural humans need to be tough to survive the day to day of back breaking farm labor. At the same time, they very rarely get formal schooling and children tend to be put to work quickly, which acts as a detriment to maximizing mental capacity.
• Making the Best: Rural humans are used to selling the best of their wares and making do with what is left over. When at market, they can choose to buy less expensive food, basic goods, and raw resources for personal use. This results in a 50% savings of the list price in the PHB. This covers leather and padded armor types as well. A rural human can always find a material for a sling, a quarterstaff, or a club at no cost.
• Rural Work: Rural humans are generally aware of human activity when they encounter it. On a roll of 1 through 3 on a 1d6, a human will know if other humans were responsible for logging, mining or farming. Further, on a roll of 1 through 2 on a 1d6, they will know, in general, if the area is good for one of those activities. On a roll of 1 on a 1d6, they can even isolate specific resources such as high quality farming soil, mineral wealth for mining, or high quality lumber for specific purposes.
• Bonus Proficiency: If non-weapon proficiencies are used, they can choose to gain a bonus non-weapon proficiency from the following list: Agriculture, Animal Handling, or Mining.

Urban

Suave and cultured, cunning and conceited - even the lowest of the low has a hustle. Urban humans tend to be more culturally aware and savvy, and careful of word and deed when they want something. Politics comes as second nature.

• Ability Score Adjustment: +1 to Charisma, -1 to Strength. Urban humans typically represent guild members, members of the Church, and nobles. They tend to learn how to navigate social encounters early on, giving them advantages to their Charisma score. However, most of their time is spent around tables or markets, and not the back breaking labor of rural or coastal humans. This reduces their overall strength.
• Cityslickers: Urban humans tend to be wealthier than other humans and demihumans. When rolling starting gold, they add an additional die before multiplication.
• Social Intuition: Urban humans can give a person a quick one over and know where they stand. On a roll of 1 - 3 on a 1d6, an urban human can assess a person's social standing. On a 1 - 2 on a 1d6, they can determine the amount of wealth that the person has, and on a 1 on a 1d6 they can assess how that person will respond to their own goals and political maneuvering. Alignment is not the question - only the actual actions of the other person. As an example, a merchant is planning on using his friendship with the Princess to secure a wool shipment contract. Concerned his plans might be known, he looks around before slipping in the back entrance of the palace. A chaotic evil bandit is hiding behind a barrel focused on getting drunk in an alley, and the merchant immediately dismisses him. A neutral good human guard has been paid by another merchant to keep an eye on him, and he senses that the guard is being shifty and following him. Concerned he keeps walking, and plans an alternative approach.
• Bonus Proficiencies: If non-weapon proficiencies are used they can choose to gain two bonus non-weapon proficiency: Etiquette and then they can choose one based on their background. If they are a guild member, they can choose a crafting skill from the General table (i.e. blacksmithing). If they are noble or a church member, they can choose heraldry, reading/writing, or an additional language. Merchants can choose from either one. [/list]

Coastal

Coastal humans are like the sea, a smooth surface with depths underneath. As with the sea, they can go from calm to raging and back to calm fast enough to make your head spin. Coastal humans are those involved in making their living from the sea or other bodies of water, be it in an urban or rural environment. If not sailors, they'll own taverns or work the docks.

• Ability Score Adjustment: +1 to Dexterity, -1 to Charisma. Coastal humans typically represent sailors, fishermen, boat builders, dock workers, and those who make their living in or around the coast. Docks or decks tend to be crowded and subject to rapid changes, making coastal humans naturally quick on their feet. However, the blunt requirements of the job, and the totalitarian nature of ship organization, makes such humans blunt and crass, and quick to anger.
• Quick to Anger: Coastal humans are used to brawls, fights, arguments, and more. Like the sea, storms brew up quickly, cause intense damage, and disappear almost as quickly as they arrived. They never shy from a fight, and are quick to join in. Over time, coastal humans learn many dirty tricks in fighting. When fighting unarmored using traditional sailor weapons (club, chain, belaying pin, dagger/knife, gaff/hook, hand/throwing axe, harpoon, scourge/whip), they gain a +2 to their AC, and a +1 to their attack rolls.
• Weather Eye: Coastal humans grow up with a weather eye, and are generally aware of what the weather will be and when it will shift (i.e. the old saying "Red in the morning, sailors take warning; red at night, sailors delight."). Even if not aware they are doing it, coastal humans will be keeping an eye on the weather subconsciously. On a roll of 1 - 3 on a 1d6, they'll be aware that a weather shift is coming ("A storm is coming" or "The storm will clear") in the next six hours. On a roll of 1 - 2 on a 1d6, they will know the specific timing of changes within 30 minutes. On a roll of 1 on a 1d6, they will know specific conditions of an upcoming storm: lightning, hail, wind bursts, tornadoes etc. On a 1 on a 1d6, they can predict the outcome of weather magic based on the changes happening to the atmosphere around them. How they use that information is up to them.
• Bonus Proficiencies: If non-weapon proficiencies are used they can choose to gain access to a bonus non-weapon proficiency from the following list: Fishing, Rope Use, Seamanship, or Swimming. Coastal humans also gain weathersense.[/list]

Wild

Wild humans are from beyond the rural environment. Lost tribes in the mountains and jungles of the world represent wild humans. Typically, they have a lower technology level compared to civilized humans - though this isn't always the case. Wild humans will tend towards tribal organization in small bands.

• Ability Score Adjustment: +1 to Wisdom, -1 to Charisma. Wild humans typically represent tribesman, or cultures that eschew the type of urban environment found in compact cities. They might represent pioneers or colonists, or hermit sects that have isolated themselves away from the main population. They tend to be patient and observant, learning from nature and the wildlands, while also eschewing contact with outsiders.
• Weapons in Hand: Wild humans need weapons to survive, and even children are trained on specific weapons from a young age. Choose from one of the following weapons: bow (short), club, dagger, javalin, sling, or spear. The character is proficient in that weapon and can make a stone or bone version (Wild Weapon, Wisdom -3).
• Survivor: Wild humans grow up learning how to live off the bounty around them. They are skilled survivalists and foragers, and can generally find everything they need close to hand. On a roll of 1 through 3 on a 1d6, they can find enough food and water to keep one person alive for a day after one hour of foraging, hunting, or setting traps. On a roll of 1 through 2 on a 1d6, they have a general direction sense, and can figure out how to get somewhere with no trails. On a roll of 1 on a 1d6, they can determine the best way to navigate difficult to pass terrain. 
• Bonus Proficiencies: If non-weapon proficiencies are used they can choose to gain access to a bonus non-weapon proficiency from the following list: Animal Lore, Direction Sense, Fire-building, Running, or Mountaineering. Wild humans gain Survival automatically.

House Rules for Campaigns

I like 2nd Edition AD&D because it is what I grew up with and what I'm familiar with. I like the Player's Option material. I like the splat books. I like the campaign settings. I like the world building. If you don't like that stuff, that is totally a'okay!

That being said, just because I like 2nd Edition doesn't mean that I don't house rule. House ruling is, in my mind, the divine right of DMs. I don't think I've ever actually met a DM that doesn't house rule. Even DMs who will go on about RAW will make a house rule in the heat of the moment - and there is nothing wrong with that! So when I find something I like from any source, I'll make a house rule to incorporate it into my game. So I thought I would share some of my house rules here, and everything here is filtered under: "In my not so humble opinion."

• Removing Class Restrictions: This one is probably one of my earliest changes. Class restrictions and level restrictions seemed stupid. The underlying assumption that it is necessary for a human-centric world is also wrong - population limitations on Elves, Dwarves, Gnomes and Halflings would work fine. If, in 100 years you have x6 human population growth, and x0.01 elf population growth, for every elf who chooses to become a wizard you'll have probably have ten or more humans making the same choice. Further, larger communities - even if outcasts - would provide for a greater pool of cooperation, debate, research and fresh perspectives meaning that human magic would probably advance faster then elven magic.
   
• Human Modifications/Dual Class Removal: The above works for the world, but for players who want to play humans and not feel like they're not getting anything, I usually provide a few boosts. For example, human characters can start the game with proficiency and a +1 to hit bonus with any one weapon of their choice. If part of a campaign setting, I usually make this cultural ("The Kingdom of Irilka has long insisted that all citizens must fight, and starting at the age of 12 under the local Guildmaster or Lord, the people train on the green or other public place in the skills of the longbow."), and provide a few options ("House Irilka's insistence on a strong yeomanry is due to the constant raiding of the Danor, their brutal lifestyle and association with orc tribes has led their people to train constantly with the battle axe as it is key to their festivals, celebrations and warfare. Only the network of fortifications keep the Kingdom safe.").
  
  Moving back to regional changes, I also worked out specific non-weapon proficiencies based on terrain types. Humans from certain terrains could choose one as a bonus non-weapon proficiency based on how humans are quick learners and can pick up a wide variety of skills. Water environments, such as ocean shores, lakes, and rivers would have fishing, seamanship or rope use. Urban environments would include heraldry, a modern language, or etiquette. These might be adjusted by social standing of course, but the idea is that the player gets an option of three NWP to choose from that are a cost of 1 and come from the General table.
  
  In most fantasy settings humans cities are often describe in typical medieval fashion compared to elven or dwarven cities: dirty, squalid, and packed to the parapet. These conditions have one natural outcome: disease. Disease often rips through human cities and kills the weak. Those left multiply and grow, having stronger resistance. Humans thus gain resistance to non-magical disease similar to how halflings and dwarves have resistance to poison and magic. They gain a +1 to their saves for every 3.5 points of constitution. The save type depends on the special attack used by the creature. Rats, for example, use the Save vs. Poison chart. If no save is allowed or outlined (i.e. rabies from a large bat) the character can make a Save vs. Poison without their bonus.
  
  Finally, I grant human intuition. Due to the constant infighting humans engage in, many humans develop an intuition about who can be trusted and who cannot be. When encountering other humans, the DM rolls a 1d6. On a roll of 1 or 2, the character will know if the person can be trusted or not. Alignment is not at question, only the actual actions of the NPC towards the PC. A chaotic evil bandit, who is more concerned with getting drunk then harming the PC will not register as a threat. A neutral good Lord who is planning to undermine the PC in front of the King will register as a potential threat.
  
  In addition, dual classing is completely removed and humans are allowed to multiclass.
   
• Unified Experience: One thing that we did do back in the late 90s was create unified experience tables. We settled on the cleric's experience table and let everyone advance using that. This was due to our feeling that though classes might have strengths and weaknesses, everyone was better off at the same level - and in general we believed in supportive play styles and didn't mind the wizard blasting everything away. It was part of the fun. Over the years I've expanded it. Using these rules:

• Rogue = Fast. For characters who meet the bonus XP requirement for their class.

• Cleric = Average. In general what all characters use.

• Fighter = Slow. If you are multiclassing, each class uses the slow table. Experience is split.

• Wizard = Very Slow. This is for characters who do not meet the class requirements but still want to be in the class.

As a final note on unified experience, another advantage for humans would be to let them use average for all classes, and demihumans can use average for any class they can go over 10 levels in normally (10+), and slow for all other classes.

What home rules do you use? How did you develop them?

"Helpful" Magical Items

The path to hell is paved in good intentions...

Magical items, in general, are helpful by definition. They actively support you in a number of ways and most players want some kind of magical item. The obvious exception are cursed items, which are intended to hurt you. The following are not cursed - they just want to help more!

The Long Arm of the Law
Generally, a +1 weapon, this is a heavy crossbow or longbow that is intended to help keep the user safe from being labeled a criminal. The magic of the weapon comes into effect when in any jurisdiction that has bans on murder.  In order to keep the wielder on the right side of the law, the weapon will not allow itself to be used to murder any sentient creature. When in such a jurisdiction, if fired at a goblin, orc, human, elf or any other sentient creature, the long arm of the law will transmute the arrow or bolt into a burst of flower pedals (50%), butterflies (25%) or a white dove that will fly away (25%). This change is permanent.

XP: 1,500

The Savers Pouch
Often made of silk and stitched with gold or silver thread, this small belt pouch is very rare. When worn, the magic of the pouch comes into effect, and 15% (gold stitching) or 10% (silver stitching) of the full value of all treasure that the character is carrying or near (that is their share) will disappear. Additionally, any coins, gems, or other monetary instruments put into the bag will also disappear. The money is completely safe from being stolen, or lost. In the event that the bag is stolen, it will return to the person who first put money into it within 2d4 days.

Withdrawing money, on the other hand, is not possible. Only when the player character reaches "venerable age" (see Player's Handbook) will the pouch suddenly burst with coins, gems, and other valuable items. In general, the player will see a compound interest of 1d4% (calculated yearly).

1% of bags include a command word, which is "Trust" followed by a person's name. The character can use this command word to target another individual as the person able to open and use the pouches contents. The character can also include conditions such as "Complete Wizard School" or "Adventure for 5 years."

There is a 5% chance that such an item is cursed, and is known as a Hedge Pouch. These pouches can have money pulled out from whenever, and by anyone who knows the command word: Distribute. Anytime the command word is said, there is a percentage gain or loss of 1d10%. Roll 1d10 and a 1d6. Even numbers are positive, odd numbers are negative. If negative, the bag will not distribute money and will instead permanently destroy  that percentage of the wealth in the bag. If the bag gets to zero, roll 1d10, and that is the percentage of the starting value of the bag that is now owed to the bag. Failure to pay will result in the bag destroying items of value before the character can touch them until the debt is paid. Then the pouch will disappear.

XP: 5,000 (Gold), 3,000 (Silver), -- (Hedge)

The Helm of Happiness
This helmet is generally made out of steel or bronze and is often carved with an eagle, kingfisher, or other large hunting bird. Two large wings of bronze and gold extend from the side offering ear protection. The helmet has powerful abjuration charms woven into it, and grants a bonus of 1 to the wearers AC. However, when the character encounters something threatening that could - potentially - make them unhappy, the true power of the helmet comes into effect. The wings flip forward covering the eyes of the wearer, and the head and neck of the bird animate and lift off the helmet. The bird begins to sing happy and cheerful tunes, modulating it's volume to exceed the volume of any growling, shouting, roaring or other unpleasant and unhappy sounds. This stays in effect until all threats are gone.

XP: 500

Demons, Devils and Demonology

First: It's been a while since my last update. My apologies as I've been swamped at work and with real life stuff. But it's good to be back!

Demons, Devils & Demonology

I understand that demons and 2nd Edition have a history. This post is not about that history but is instead about ignoring all of that history and introducing a concept I think could provide useful story tools for DMs moving forward. Demons and devils were included in 1st Edition and not 2nd due to that history, but this post is not about the demons and devils in 1st Edition. These rules are going to go in a different direction.

These rulers were inspired by the book "Scales of Justice" by Daniel Hood. the fourth book in the Fanuilh series.

Librum Daemonum

Mara peaked through the dirty glass into the basement. There, the Circle of the Broken Blade had gathered around a circle drawn in chalk. Chained in the center was a sacrifice, a small goat from the fields behind her. She frowned as she studied the circle. Reaching into her bag she pulled out an oil cloth wrapped book. In the light from the window the words 'Librum Daemonum' were clearly imprinted in the red leather of the cover. She opened it and started flipping through pages, her eyes darting from diagrams back to the chalk circle inside. She found it nodded to herself. Packing up she backed away slowly from the building and went around to find her friends, the Circle was looking for information - more than likely about Mara and her friends.

The Book of Demons is a rare tome that seems to turn up where mischief is desired. Trade in the books is generally considered illegal, and when found the books are burned. Only certain wizards and clerics are allowed to openly own them, as they are responsible for tracking and killing those that summon demons and the demons themselves. Despite this prohibition, copies can still be found in private collections even if they are not used. Simply owning them is a thrill. Yet, in the back of the dustiest shops in unexpected nooks it is possible to find someone who, with the right incentive might be able to provide a copy of the book. 

The books themselves are surprisingly uniform. They are always bound in red stained leather, with the words Librum Daemonum in white. Touching the letters shows that it is bone embedded into the leather itself. The book is usually between an inch to an inch and a half thick, with crackling parchment pages. They almost always look aged.

The inside of the book is written in black ink and is composed of diagrams, formula, and descriptions of the demon and devils that can be summoned and what it is that they do. The language is an ancient form of denomic, and the user of the book must either be proficient in the language ("Languages, Ancient"), or spend 3d4 weeks studying the manuscript, where after it will be added as a bonus non-weapon proficiency. This proficiency can be improved per normal,

When someone is seeking one of these books for a specific purpose - especially if that purpose is dark - then when they find a copy and open it for the first time, it will often fall open to the specific summoning circle they need as a form of temptation.

Summoning a Demon

Hald, a balding gnomish warrior slammed the door with his shoulder. Despite his small size, he was exceptionally strong - and the gauntlets of ogre's strength didn't hurt. As the door crashed open, the Circle turned in shock their chant falling away in surprise. The leader, caught up in the summoning, continued his chant unaware of the sudden commotion. Mara was only a few steps behind and with a flick of her wrist, she launched a knife at the cultist near the front. Hald was already pushing forward wielding his heavy battle axe in two hands as he closed towards the circle. They pressed hard, as they only had a minute or two before the demon arrived.

The book describes how to summon multiple different types of demons for multiple different purposes. Anyone can use the book to create a summoning circle. Each book is divided into 10 overarching spheres of influence:

1. Foresight: Portents, Omens and Divination | Internal
2. Promises: Power, Deals, and Contracts | Internal
3. Deception: Secrecy, Deceit, and Trickery | Internal
4. Knowledge: Information, facts, and history | Internal
5. Bloodlust: Hunting, killing, and battle | External
6. Vengeance: Revenge, hatred, and envy | External
7. Assassination: Destruction, death, and power | External
8. Confusion: Obstruction, plots, and manipulation | External
9. Pestilence: Disease, famine, and vermin | External
10. Hedonism: Desire, debauchery, and lust | Internal

If a sphere of influence is External or Internal indicates where the demon or devil will be summoned outside of the summoning circle (External, with the caster standing inside) or inside the circle (Internal, with the caster standing outside of the circle). When summoning, the caster has to create the circle. Creating and summoning is like casting a spell, though the level of the spell is determined by the rank of the creature that you are attempting to summon.

The ranks are as follows:

1. Tempters: (HD: 1 - 3)
2. Masters: (HD: 4 - 7)
3. Minor Lord: (HD: 8 - 11)
4. Lord: (HD:: 12 - 14)
5. Duke: (HD: 15 - 17)
6. Dark Champion: (HD: 18 - 19)
7. Prince of the Sphere: (HD: 20)

Determining what kind of demon responds to the call is handled by percentages. There is a 60% chance a demon will show up for an external sphere, and a devil for an internal sphere. If a demon, there is a 60% chance it is a fighter type character (treat as a PC fighter where level is the HD), and 20% chance it is a wizard, 10% chance it is a thief, and 10% chance it is a cleric. If a devil, there is a 60% chance it is a cleric, 20% chance it is a thief, and a 10% chance it is a fighter or wizard. HD are rolled randomly. They are always humanoid type creatures. 

Each summoning circle is generally the same:

Summon Demon or Devil (Conjuration/Summoning)Range: 20'
Duration: Special
Area of Effect: 20' radius
Components: V, S, M
Casting Time: 1 to 20 Turns
Saving Throw: None

The summon demon spell found in the Librum will take between 1 and 7 turns to cast depending on the HD of the creature being summoned. This does not include the time to set up the summoning circle, which requires materials ranging from common for low ranking demons to exceedingly rare for Princes. While a goat or chicken might do for a tempter, an angel or high priest will be needed for a Prince. Stopping the summoning of a Prince might be an adventure in and of itself. 

Controlling the Summoning

When summoned, a demon is not under any special power or control of the caster. The summoning circle will either protect the caster by presenting a barrier. An encounter check is made immediately. Demons start off as threatening. If the summoner has less hit dice then the demon, it changes to hostile. If the summoner has more, it changes to indifferent. Devils start off as indifferent, if higher in HD, they are threatening. If lower they are friendly. Princes are always hostile.

When starting the encounter roll 2d10 and subtract the reaction adjustment of the summoner based on their charisma score. Devils are always lawful, demons are always chaotic. If the player's alignment matches the summoned creature, then they get a +1 bonus to their reaction adjustment. If the summoner is not matched, it is a -1 bonus. Other bonuses and penalties can be found on Table 50 in the DMG for encounters.

The demon does not have to stay in the summoning circle and can simply leave and return to where it came from. This happens automatically if flight is the encounter result. Spells that bind demons can be applied in this situation, though this automatically sets all future summons to hostile.

When the demon arrives it will be prepared to help the summoner answer their question and will stick around long enough for one attempt. They will either be ready for battle with appropriate gear, will have the right spells memorized, or will have access to the right non-weapon proficiencies.

By their nature, demons and devils in general are unhelpful. If the question is to uncover where Baltur the Money Lender hides his account ledger the responding creature might give an exact location ("The third stair in the west wing of the manor has a hidden compartment") or might be more mysterious ("Where feet tread upwards towards the setting sun, the count of Hydra will reveal a light within the darkness.").  The level of help from the creature is dependent on their reaction. Friendly creatures will be more helpful.