Ry'Cansubyth, Soul Hound

Deathtouch, indestructible, protection from instants and sorceries, leach (When this creature enters the battlefield, you may sacrifice a creature, if you do X becomes that creatures converted mana cost.)
When Ry'Cansubyth, Soul Hound enters the battlefield, create X 3/3 Hound creature tokens.
Sacrifice a creature: Target creature gains +X/+0
"A rush of wolves and death follows his howl"