Ashiok, Harbinger of Horror

Whenever a creature you control dies, you may exile it from your graveyard. If you do, target player creates a token that's a copy of it. The copy is
a Nightmare in addition to its other types, and can't
be sacrificed.

Whenever a Nightmare deals combat damage, draw
a card. Then if that combat damage was dealt to
you, Ashiok deals that much damage to any target.

Not all nightmares can be escaped by waking.