Unknown Armies uses a percentile dice system where checks are made by rolling two 10-sided dice, with one representing the "tens" and the other representing the "singles" digit (d100 for short). Players aim to roll under their appropriate skill in order to pass their skill test. However, it is unlike standard systems in that the higher the roll obtained the better the result (while still keeping under the skill level).
Players can start off as mundanes, Avatars, or Adepts. The benefit of the latter two is that one finds themselves in tune with some mystic force, and are most likely clued in to the Occult Underground. An Avatar is a person that channels an "Archetype", a powerful and universal role in culture. Examples include the mystic hermaphrodite, the hunter, and the demagogue. Adepts have spells related to certain obsessions, and must power themselves with related activities. However, playing mundanes also has its advantages as one can spend their points on aspects other than an Avatar's or Adept's power.
Each character's statistics are split into 4 main categories:
- Body – deals with main physical skills
- Speed – deals with dexterity based skills
- Mind – deals with mental skills
- Soul – deals with personality and "spiritual" based skills
The system is considered flexible in that players can choose their own skills.
Each player's character also starts off with an obsession (something the character is passionate about) and assigns a relevant skill. (For example, an obsessive stamp collector will most likely have the appraise skill as an obsessive skill.)
The system also introduces the concept of flip-flopping, where players who are using their obsession skill can choose to switch the "tens" and "singles" of their dice rolls (for example, turning 74 into 47.)
There are also 5 madness meters, which help catalogue your character's sanity:
- Violence – Represents your character's reaction to violent acts
- Unnatural – Represents your character's reaction to the unnatural
- Helplessness – Represents your character's reaction in helpless situations
- Isolation – Represents your character's reaction in periods of isolation/loneliness
- Self – Represents your character's ability to deal with issues relating to identity
Source: Wikipedia, "[en.wikipedia.org/wiki/Unknown_Armies Unknown Armies]", available under the CC-BY-SA License.