Kylith, Lord of Vengeance

Nightmare, Shadow(Whenever a creature with Nightmare attacks, tap target creature)
Whenever you sacrifice a creature, add a +1/+1
on target creature. Whenever a nontoken Shade creature you control dies, create a 3/1 shade
creature token with flying and decayed.
"Shades are creatures of Vengeance, and call the
Abyss home. All you can do fight one is to hide."
-Journal of Valik.