The chronurgy wizard in our group met a former research partner of his, who had gone mad after seeing both the beginning and end of time. He offered to share this knowledge with the wizard if he killed the rest of us. The session ended there though since wizard needed to leave.
The wizard joining up with his former partner turned out to be a smooth way for the wizard player to bow out of the campaign though, so it's not all bad.
Or just revive them. Death isn't that big a deal in D&D.