Pyretic Study

Whenever a land enters the battlefield under an
opponent's control, that player may pay {2}. If
the player doesn't, exile the top card of your
library and you may play that card until the end
of your next turn.
At the beginning of your precombat mainphase,
add {r} for each card exiled with Pyretic Study.
Spend this mana only to cast cards exiled with
Pyretic Study.