Chainer, Dementia Master

All Nightmares get +1/+1.
{B}{B}{B}, Pay 3 life: Put target creature card from a graveyard onto the battlefield under your control. That creature is black and is a Nightmare in addition to its other creature types.
When Chainer, Dementia Master leaves the battlefield, exile all Nightmares.

Ghoul's Feast

Target creature gets +X/+0 until end of turn, where X is the number of creature cards in your graveyard.

Soulshriek

Target creature you control gets +X/+0 until end of turn, where X is the number of creature cards in your graveyard. Sacrifice that creature at the beginning of the next end step.