By the end of the campaign several of the major characters we'd met along the way turned out to be my character in disguise. One of the factions we were fighting with also had access to time travel and they didn't care about the integrity of the timestream (they were trying to destroy existence entirely) so they'd go back in time and try to interfere with our history to erase us by killing important questgivers and whatnot. I'd have to go back in time and impersonate them, giving ourselves those quests to ensure that our history continued playing out as it always had.

I was the party member with the best deception skill so I was the designated historical figure stand-in of the party.