Rubeus, Master Thief

Flying
At the beginning of each upkeep, Exile the top
card of that player's library. You may play cards
exiled with Rubeus, Master Thief . If you do,
pay life equal to that cards mana value rather
than paying it's mana cost.
Whenever you cast a spell, if you don't own it,
the owner of that spell sacrifices a creature.