Chainer, Dementia Master

Nightmare creatures 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.
All Hail, The Lord of Nightmares.