The design calls for a resolution mechanic that simulates a normal distribution, which when graphed looks like a bell curve. This means at least three dice must used. A dice pool using 3d6 is currently the chosen configuration. The 3d6 dice pool has a range of 3-18 and a mean of 10-11. A strong reason to use the 3d6 dice was for ease of determining Difficulty Ratings (working from a mean result of 10).