Kalthiel, the Silent Angel

Flying, indestructible
Kalthiel, the Silent Angel can't attack or block unless you control a creature with a +1/+1 counter on it.
Other creatures you control have undying.
{w/b}, Tap an untapped creature you control with a +1/+1 counter on it: Target player loses 1 life and you gain 1 life.
In the end, all bow to death.