Urza, Grand Artificer

{u/r},{t}: Put an artifact card from your hand onto the battlefield. Sacrifice the artifact at the beginning of the next end step.
If Urza, Grand Artificer would be put into a graveyard from play, if you both own and control him, an artifact named The Mightstone, and an artifact named The Meekstone, exile them, then meld them into Urza, Planeswalker at the beginning of your next main phase.