Cortex System

The Cortex System is a family of related tabletop role-playing games built on one dice mechanic. Every trait of a character, whether an attribute, skill, relationship, power or distinction, is rated by a die size. When a player acts, they pick one trait from each relevant set and roll the dice together as a pool. Dice that show a one are hitches that mark something going wrong, the two highest results are added for the total, and one more die is set aside as the effect die that decides how much the result achieves. Players also spend plot point tokens to roll extra dice or add results. The system grew from Sovereign Stone and became the house system of Margaret Weis Productions, used for Serenity, Battlestar Galactica, Supernatural, Smallville, Leverage and Marvel Heroic Roleplaying, before Cam Banks unified the earlier versions as Cortex Prime.