Yil-Zothur, World-Dreamer

{t}: Add {c} to your mana pool.
This card enters the battlefield tapped.
When this card enters the battlefield, sacrifice X
lands you control. X can't be 0.
On your upkeep, mill X, pay X life: if a land card
is revealed this way, you may play lands from
your graveyard this turn. This card's power and toughness are equal to the number of lands you control that can produce {c}.