Muulbein, Contract Savant

Whenever an opponent pays life, you may search your library for a creature card with converted mana cost X and put that card onto the battlefield, where X is the amount of life that player paid. If you search your library this way, shuffle it.
Whenever you cast a noncreature spell, target opponent may pay X life, where X is equal to that spell's converted mana cost. If that player does, counter that spell.