Merieke, Accursed Maiden

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Merieke, Accursed Maiden doesn't untap during your untap step. Whenever a creature you control dies, you may pay 2 life. If you do, untap Merieke, Accursed Maiden.
{t}: Take control of target creature. It has Prowess as long as Merieke, Accursed Maiden is tapped.