Uxar, the burial minder

Uxar, the burial minder power and toughness
are each equal to the number of legendary cards
in all graveyards and command zones.
Whenever Uxar, the burial minder attacks,
defending player mills two cards.
Whenever an opponent mills one card, you
may pay {1}{g}. If you do, Uxar, the burial
minder gets +X/+X until end of turn where
X is that card converted mana cost.