Decayborn Muse

At the beginning of each player's upkeep, that
player exiles the top card of their graveyard until
they exile a land card. They may pay X life,
where X is the number of cards exiled this way.
If they do, they put that land onto the battlefield
tapped under their control.
{3}: Target player mills X cards, where X is the
number of cards you own in exile.