While there are several ways to make everybody lose the game or force a draw, this ability is the only way to make everybody at the table win
Entering as a copy of any creature card from any graveyard, its flexible, reactive, and full of surprises
Lower numbers are generally more exciting, but if you open the biggest number in a run (like a 500/500), thats usually worth more than a middling number, too
Conversely, if my hand isnt full of counterspells early on, Im going to keep the Mentor in my hand and let them think they need to keep sculpting
That said, the symmetry is a bit of a drawback, because opponents get the same haste boost, so its at its best when you plan to explode first and close the door fast