The New World of Darkness system uses dice pools for each and every action that requires a roll. Nearly all die pools follow the basic formula:
Attribute Rating + Skill Rating + Equipment Modifiers + Situation Modifiers
Attribute Rating is the number of dots you have in an Attribute. Each dot adds one die to the dice pool.
Skill Rating is the same as above, only with a Skill. Having a Specialty in a skill grants you one additional die to your die pool when a roll with that Skill involves the Specialty.
Equipment Modifiers are relevant pieces of gear that add or subtract to your pool. Having a fake FBI badge when trying to intimidate someone might add one or two dice to your pool. Trying to open a locked door with a set of improvised lockpicking tools might subtract one or two dice from your pool.
Situation Modifiers are things about the environment or particular circumstances that may give you bonuses or penalties. Trying to sneak up on someone in a crowd would give you a bonus. Trying to grab onto a monster when he’s coated with slippery grease would give you a penalty.
When your pool has been assembled, roll it. Any dice that come up as an 8, 9, or 10 are counted as a success. If you roll at least one success, you succeed on the action. Otherwise, you fail. Failing a roll rarely has fatal consequences and is more often a temporary or slight setback. Rolling five or more successes constitutes an exceptional success, which has additional beneficial effects.
Rolling a 10 is actually really good, because it means that the die “explodes” and can be rolled again for potential additional successes. This is called the 10-Again rule. When you make your roll, reroll any dice that come up 10. Any additional successes you roll are added to the total. If you roll more 10s, keep rerolling until they no longer come up 10.
It is possible to get the 9-Again or 8-Again property on rolls. This functions exactly like 10-Again, only with the numbers 9 or 8 instead.
Here is an example of a basic roll:
Xander, the Green Ranger, decides to try and talk down a monster that the Rangers have encountered while out on patrol. The Storyteller tells him that in order to get the monster to listen, Xander will have to make a Presence + Expression roll to make his case.
Xander has three dots in Presence and four dots in Expression. He rolls a total of 7 dice, and they come up: 3, 7, 2, 8, 5, 8, 10. Since three dice came up as 8 or more, that’s 3 successes. Since he rolled a 10, Xander rerolls that die and rolls a 9. That’s another success, giving Xander a total of 4 successes on his attempt. The Storyteller rules that, while not entirely convinced to stop his rampage, the monster will at least pause and listen to what the Rangers have to say.
If enough modifiers apply to reduce your pool to 0 dice or less, you can still try the action by rolling a single die known as a chance die. This die functions differently than the others: rolling a 10, and only a 10, is a successes, and the 10-Again rule applies as normal. Rolling a 1 (while having no successes) means that not only did you fail, you failed spectacularly. This is called a dramatic failure, and it means that the Storyteller gets to screw you over.
Later in the scene, Xander and the other Rangers are on the run from the monster, who has gotten unexpectedly violent. The Rangers have to jump across rooftops in order to escape him, so the Storyteller tells everyone to make Strength + Athletics checks to attempt the jump.
Xander, while good at talking, is not so good at jumping. He only has one dot in Strength, and one in Athletics. However, due to some recent rainfall, the roofs are slippery, so the Storyteller imposes a -2 die pool penalty. Xander’s die pool is now a chance die. Rolling, it just isn’t his lucky day, and the die comes up 1 – a dramatic failure. The Storyteller rules that Xander slips right before making a jump and falls over the edge of the rooftop, which is four stories above the unforgiving pavement. Uh oh.
Actions in World of Darkness are divided up into a few categories: Instant, Opposed, and Extended.
Instant actions take a single roll, and usually are a single effort. Throwing a punch, avoiding a laser blast, and jumping over a gap are all instant actions. These are actions that can be accomplished in a few seconds.
Extended actions take a little bit longer and comprise multiple die rolls in succession. These are things like doing research at a library, talking down a monster with hostages, or repairing the Zords are all examples of extended actions. Rather than simply getting one success, each roll comprises an amount of time, and the Storyteller has secretly determined a number of total successes you must meet. Each roll adds to the total number. So, each roll involved in fixing the Megazord might take 30 minutes. A simple tune-up or check-over might be three or four successes, while something like overhauling the controls or major repairs might be 10.
Contested actions can be either instant or extended, but they are always two or more characters seeking to do something faster or better than the other(s). The one who gets the most successes (or reaches the total fastest, in the case of an extended action) is the winner. Arm wrestling is an example of an instant contested action. A long-distance sprint to reach a finish line first is an example of an extended contested action.