Aleko, Diviner Warden

At the beginning of each end step, exile target noncreature, nonland card from the graveyard of the player whose turn it is with a shimmer counter on it.
Once per turn, you may cast a card from exile if it has a shimmer counter on it and you may spend mana as though it were mana of any type to cast that spell. If you cast a spell this way, remove a shimmer counter from that card.