Skull of Corruption

Whenever a creature dies, put a dream counter
on Skull of Corruption. You may remove X
dream counters from Skull of Corruption to
create a token that's a copy of the exiled creature,
except it's a Nightmare in addition to its other
types and it has "Whenever this creature deals
combat damage to a player, that player exiles
that many cards from the top of their library."
I've seen the true nature of dreams, and it is not
pleasant.