It was amazing just how unlike them their +40 self was and they had no idea that was how they were going to be. Yet this weird little not-dead elf seemed to know so much, too much.

Or he was an elaborate liar. They want to rule that out. They can't believe or dismiss what he has to say without ruling that out.

"Provide me a fact that only someone from the future would be able to know." They demand, watching him for how he'll react to the demand.