Quote Originally Posted by Quertus View Post
Yeah, Time Travel certainly does seem like a game-changer. I'm not really sure that Dr. Who time travel is anywhere near the top of the food chain here, though - the Doctor seems to have issues with messing with time once he's already in the middle of events. Which will be the case for this challenge.
Doctor Who has established that the reason that you don't try to do things like crossing your own timeline or unmaking your enemies before they were created or the like is that you're liable to create a planet-destroying paradox or shatter the fabric of a galaxy or something similar; misuse of time travel is very bad at solving problems, and very good at creating them. Since the Doctor does not, as a rule, want to break reality, they try to avoid doing that. (It has still happened a few times, mind you!)

However, we also know that it is possible to survive these things, because that's what happened in the Time War - the Time Lords and the Daleks both stopped playing by those rules and tried to retroactively destroy each other, except that they were both time travellers so they survived, and then things got bad. So bad that entire swathes of time were wiped out of existence, thrown into nightmarish repeating paradoxes, doubled-up on each other, and so on. The war only ended when the Doctor obliterated both species entirely from the timeline, undoing most of the damage that they did.

I think that's about as powerful as time travel can get before it moves into the "infinite capability" zone, honestly; you can make whatever changes you like, but if you make the wrong ones you blow up everyone you were trying to save. Of course, if your goal is the eradication of every other universe, blowing up their universe while making alterations to it isn't such a net problem.