Impeach

Suspend 6 - {1}{b}(Rather than cast this card
from your hand, you may pay {3}{b} and exile it
with 6 time counters on it. At the beginning of
your upkeep, remove a time counter. When the
last is removed, cast it without paying its mana cost.)
Exile all legendary creatures target player controls
that are red, white, and/or blue