Edgar's Blood Ritual

(You may cast a legendary sorcery only if you control
a legendary creature or planeswalker.)
You may sacrifice a creature. If you do, put a
+1/+1 counter on each creature you control.
They gain haste and lifelink and are black
Vampires in addition to their other colors and
types.
Centuries ago, a demon offered an alchemist a way
against a famine.