I remembered that once in the past I played a game that you could reset your levels infinitely, MUOnline. The game was very boring, but what kept people playing was the fact they could play forever, and level up forever.

But resetting entirely on Anni would be insane, so, after seeing d2pk tokens I came up with an idea:

A token sold by hadriel (for gold or for free), that requires lvl 99 to use and resets the level to 98, and experience to lvl ZERO, so the player can get that last level more times, as long as the player farms that 3.5 bi exp from scratch again.

If it's still too easy, it could set an invisible negative exp% bonus to the character.