Velcyra, Broker of Pain

Double Strike, Lifelink
Extort (Whenever you cast a spell, you may pay {w/b}. If you do, each opponent loses 1 life and you gain that much life.)
{t}, Sacrifice a creature: Target creature or player takes damage equal to the sacrificed creature's toughness. Put a hit counter on Velcyra, Broker of Pain.
At the beginning of your upkeep, if Velcyra, Broker of Pain has three or more hit counters, you may transform her.