The Ultimate Riddle????

I’m really not sure anything about this one.

We know the Ultimate Reward is creating a new universe, and I believe ruling over it in some capacity. It follows that the Ultimate Riddle would be related, but the URe is not the answer to the URi. I figure the URi has something to with the personal growth of the characters, the nature of free will when inevitability is brought into consideration, but…yeah I just really don’t have any idea.