Shilgengar's Price

As an additional cost to cast Shilgengar's Price, sacrifice an Angel.
Put a vampirism counter on each Human you
control. Change all text of those creatures by replacing all instances of the Human creature
type with Vampire, and those creatures gain
lifelink. Then put X +1/+1 counters on each
Vampire you control, where X is the converted
mana cost of the sacrificed Angel.