original idea by ejh
The following is an alternative to Mythic RPG, which contained a section on how to roleplay without a gamemaster.
To determine if something is true, one rolls 1d100, and checks this chart. This is called "consulting the Oracle."
Before making an Oracle Roll, the players should agree on a base Likelihood of the answer being "yes," based on everything they know about the situation which is not explicitly codified as a Theme or Fact (see below). It's a big ol' guesstimate, and all that matters is that the players more or less agree on it.
And so on from there in either direction.
Base Likelihood is modified by Themes and Facts and their Relevance.
Not everything that is the case in the game world has to be written down in so many words, but key facts should be. These key facts can include the capabilities of the characters (see "attributes and skills" in traditional RPGs), and anything in the character and nature of the world around them. Facts are often established by means of Oracle rolls (which may be influenced by other Facts...)
One may never contradict a Fact. If the answer to an Oracle question is already implied by a Fact, that answer is an automatic "yes" or "no." No roll. However, usually, facts do not imply other facts, they only suggest them. If someone is rich, that doesn't imply they drive a nice car, it only suggests that they are likely to.
Facts have a numeric value. The default value for a Fact is 1, but for facts which represent something that is going to come up often and may vary quantitatively, they may be assigned any low positive value (usually 1-3, but possibly higher). For example, in a game with a lot of combat, the Fact that someone has Fighting Ability may be indicated as having a value of 1, 2, 3, or more, to indicate degrees of fighting ability along a scale. NOTE: In Risus terms, the numeric value of a fact will be defined by the potency of a cliché.
Themes are basically Facts which never imply anything, they only suggest things.
They tend to concern intangible things about the story, not tangible facts in the game world. For example, the Theme "Sword & Sorcery" might exist, describing the world in general, making any event which is in keeping with the Sword & Sorcery genre (as understood by the players) more likely. Or more personally speaking, a character might have the Theme of "comic relief" attached to him, suggesting that he is unlikely to either suffer great tragedy or achieve anything very heroic, and influencing Oracle rolls where either of those are about to happen. Facts are things that objectively exist in the world; Themes are metagame -- about the story told in the game.
To start with, each character can have at least one Theme for free, and players may establish as many Themes at the outset that they like concerning the world. Any non-player character or thing in the world which is important to the players can have a Theme established concerning it, though probably not every one will.
Relevance is the degree to which a given Theme or Fact matters for an Oracle roll. It has to be guesstimated/eyeballed, just like Base Likelihood, for any given roll.
If the Fact or Theme doesn't have a numeric value attached to it, just add its Relevance to the Base Likelihood. If it has a numeric value, multiply the Relevance by the numeric value. (i.e. if I have "Strong (2)" and I'm trying to open a stuck door, for which the Relevance of my strength is -10, I have a -20 to add to the base Likelihood of my opening the door.)
Redundant Facts should not be included multiple times in the same Oracle roll. If your character has a Strength fact and a Warrior fact and is trying to open a stuck door, you couldn't use both of them because "well, warriors are strong." That's already there in the Strength fact.
Once appropriate modifiers have been added to Base Likelihood, roll the dice. After adding the modified Likelihood to the dice roll, read the result off the Oracle table.
Starting The Game
To start the game, you should describe your character(s), using a paragraph, a list of Facts and Themes, or both. You should also describe the world, and the opening situation, using the same techniques: a paragraph or so, and Facts and Themes. (You can go into as much or as little detail as you like here.) To give the story some momentum, the opening situation should be a "kicker" in Ron Edwards' sense -- something which is going to change your character's life and to which he or she must react somehow.
If multiple players are playing, they should include in the "world/opening situation" part whatever they can all agree on.
From then on, you tell the story.
You can make your character do, or attempt, anything you want. Whether your character succeeds at what they try depends on Oracle rolls. What happens outside your character's control depends on Oracle rolls too, but it requires you to initiate questions. If you never ask an interesting question of the Oracle, nothing interesting will ever happen. If you ask a lot of interesting questions, a lot of interesting things will happen.
Adding New Facts
You can ask a question about a new Fact or Theme to be added to the list -- after all, facts and themes are nothing but a formalized statement of important elements of the game world. Assign that Fact or Theme a likelihood of being present, and make the roll.
You can also use Oracle rolls to get rid of existing Facts.