Castle Kayn, Seat of Pain

Castle Kayn, Seat of Pain enters the battlefield
tapped unless each opponent lost life this turn.
{t}: Add {u}, {b}, or {r}.
{2}, {t}: Add {u}{b}{r}. When you cast your next
spell this turn, each player mills 1. Then, for
each other player, exile a card from that player's
graveyard. If a nonland card is exiled this way,
that player loses 1 life. If no life is lost this way,
untap Castle Kayn.