100DOS is a custom-made tabletop roleplaying game system designed to be modular and all-inclusive. The main game that 100DOS is used for is Mythic, a fan-made Halo tabletop roleplaying game.

Mythic is not only a massive game with almost all of the content you could ever wish for being present, but there are also over a dozen expansions of varying sizes.

From Medieval warfare to modern warfare, from Titanfall to Gears of War, and much more. New magic systems, expansions for economics, weapon customization, and space combat. 100DOS offers anything you can think of, including giving you the development tools and tutorials to make your own content.