I'm fine with the concept of someone being kidnapped and used for a failed ritual summoning, becoming fused with an eldritch abomination. But time is a bit of a no-no. There's really no real way to having a time power that works in a roleplay setting. I'm fine with sharp corner teleportation and the abomination itself having time powers, but not really a player character. Also, time traveling NPCs is a can of worms that I don't want to ever have to open, especially for something that'd be nothing more than a side-story.
I'm with you there. I almost typed in that time travel is a big no-no for me but omitted it for reasons unknown (was pretty tired last night while editing my post.) The only sort of time related powers I will ever touch (unless a setting has time travel be a common theme, that's different) are things like being able to detect when something is disrupting the flow of time, or some inherent resistance to paradoxical events.