Mirror, Mirror on the Wall

Fairest of them all — Black creatures you cast cost
{b}{b} less to cast.

Whenever a creature you control enters the battlefield, each opponent loses 1 life and you
gain 1 life.

"Famed is thy beauty, Majesty. But hold, a lovely maid I see. Rags cannot hide her gentle grace. Alas, she is more fair than thee."
—Magic Mirror