The 2d20 system is a dynamic, narrative system, designed to produce varied and interesting results from dramatic and action-packed situations. Characters roll two d20s, attempting to roll as low as possible on each one – the more dice that roll low, the more successes the character scores.
Tasks will require one or more successes to be successful, and any successes scored beyond that minimum become Momentum, which can be spent to achieve a variety of advantageous effects. However, this can come at a cost: characters who wish to succeed can push their luck, rolling extra d20s to boost their chances of success and the Momentum they generate. However, each extra d20 comes from the character’s resources – such as stocks of arrows – or adds to a pool of Doom that represents all the things that can go wrong in an adventure, which the GM can spend to complicate adventures and scenarios and make the characters’ lives interesting.
System used in Mōdiphiüs Entertainment's Mutant Chronicles 3rd Edition Roleplaying Game, Infinity the Roleplaying Game, and Robert E. Howard's Conan: Adventures in an Age Undreamed Of games.