[@AtomicNut]
Clairvoyant has a range limit. I'm fairly certain about that. Claire porting away from the Clairvoyant interrupted their communication, so it appears that she does have limits.

But the Prescient's ability has nothing to do with distance. They would see the defeat of the High, and work backwards from there. They would know who did it, and could then observe everything that person did in their lifetime. They would know that this person did something with the Starbursts, and where and when that person was born. Then they would simply stop that person from being born. Wouldn't even have to kill them, just distract the father and make it so he married someone else. Or strongly advocate birth control to them.

Of course, this is assuming that the Prescient's powers of prescience are truly limitless. Perhaps it's true that there are things they can't predict. After all, they are the most mysterious and most powerful of the High. Who knows what they can and can't do? But that's one of the problems with fighting them.