Tycho is one of the three original AI's that were on-board the UESC Marathon. While Tycho has little interaction with the story in Marathon (Game) and Marathon 2: Durandal, he plays a much larger role in Marathon Infinity.
The UESC Marathon's science AI, Tycho, features only briefly in the first two games. In Marathon, Tycho was initially thought to be destroyed by the Pfhor but was captured by them and re-conditioned into Rampancy.
In Marathon Infinity, during the second timeline, he kidnaps the player and uses him as a tool to take control of a Pfhor fleet as the first chapter of the game. Cruel and bitterly sarcastic, Tycho is probably the least sympathetic character in the game.
"Durandal thinks that he's so smart, but he doesn't realize that I've been following him around for the last eleven years, after the Pfhor stopped trying to dissect me. You're looking at the bug fleet's resident expert in AI counter-insurgency. Notice the lack of compilers on board? That's not by accident; my new ship has quite the effect on their collective unconscious. Now that my brother approaches, we will set about turning everything against him, Hamlet and his uncle, only I'm not crazy."
- Marathon Infinity, Rise Robot Rise, first terminal
- Tycho may have been named after Tycho Brahe, a 19th Century philosopher.