Aldritch the Devourer

Whenever a card enters your graveyard, you may choose to exile it. If you do, put +1/+1 counters on Aldritch the Devourer equal to half that card's mana value rounded down.
At the beginning of your end step, you may remove all +1/+1 counters from Aldritch the Devourer to create a x/x Carcass token, and make all players lose x life where x is the amount of +1/+1 counters removed from Aldritch the Devourer this way.