Vex, the Gloomist

Whenever another creature you control dies or is
put into exile from the battlefield,you get an experience counter.
At the beginning of your upkeep, choose target instant, sorcery, or enchantment card in your graveyard. If that card's mana value is less than
or equal to the number of experience counters
you have, you may cast that spell without paying
its mana cost. Otherwise, put it into your hand.
If a spell cast this way would be put into your graveyard, exile it instead.