From the introduction: The pass/fail dice roll is a central component of roll playing games. In the 45 years of the development of the hobby, multiple systems have come about. The purpose of this essay is to cover the basics of dice roll mechanics for multiple systems so that the reader can clearly understand how they work. Specifics of stats, attributes, skills, modifiers and conditions are intentionally avoided. Also, except where it is integral to the core mechanic, damage and criticals will not be covered. This is not an exhaustive list. It is a list of what is at the time of writing the most talked about systems and some of the more unique or unusual systems. User summary: The essay specifically looks at these games/systems: d20 System Dungeons & Dragons (5th Edition) Cypher System Open Legend 2d20 System GURPS Shadowrun Shadowrun: Anarchy Savage Worlds Call of Cthulhu The World of Darkness Fate Core Rifts Powered by the Apocalypse Genesys Year Zero Engine Rolemaster Game System Castle Falkenstein Traveller GUMSHOE