Robb Stark, the Boy Wolf

Legendary creatures you control get +X/+X, where
X is the number of legendary creatures you control.

Whenever you cast a legendary spell from your hand,
exile cards from the top of your library until you
exile a legendary nonland card with lesser mana
value. You may cast that card without paying its
mana cost. Put the rest on the bottom of your library
in a random order.