Vikings plunder jewelry stores along the waterfront! Killer robots from the future hunt Abraham Lincoln! And the heroes are on trial for crimes they haven't committed... yet! Time is a toybox for superheroes and villains, filled with colorful characters and convoluted plotlines. Time travel opens up new potential just as much as blasting off into space, with the convenience of all the major players and events already being written for you! With time as a canvas, you can pump up the grim or gonzo in your adventures, or build a whole campaign around protecting not just the world, but everything that has happened or ever will happen! The Time Traveler's Codex is a supplement for Mutants & Masterminds, Third Edition that launches heroes into the fourth dimension. The Time Traveler's Codex includes: A brief history of time travel, and an overview on the structure of time and how it functions in the Earth-Prime setting. Tips for deciding how time travel works in your campaign, complete with the consequences and hazards of meddling. Advice on creating your own time-hopping series, including optional rules, suggested power levels, and temporal dangers that lie along the way. Six causality-shaking villain archetypes who can harry heroes across the centuries, like the Immortal Conqueror and the Future Perfectionist, backed up by dozens of minions from across time and beyond! Guidance for players building time traveling heroes, complete with new advantages, powers, and equipment as well as a half-dozen time-sliding hero archetypes, like the Quantum Alien and the Temporal Tourist! Over a dozen different historical eras detailed, with rules guidance and statblocks for each, as well as adventure ideas and guidance for setting individual adventures in that time period, or an entire campaign! Catapult your adventures out of the city streets and into medieval French castles, Aztec battlefronts, and the imperial Ming court with the Time Traveler's Codex!