GLaDOS, Aperture's Overseer

Eminence — At the beginning of your upkeep,
look at the top card of your library, if is a land
card, revel it, then put it in your hand, otherwise
exile it face down and put a room counter on it,
you my cast exiled cards with room counter on it,
cards with room counters on them cost {1} less
to cast for each exiled card with a room counter.
{5}{t}, exile targeted non-land permanent an
opponent controls, then put a room
counter on it.