Ragnarök

(When this card enters the battlefield, put three event counters on it.)
When a "Loki" card you or your opponent
controls is exiled, remove one event counter.
When a "Jormungandr" creature you or your
opponent controls leaves exile, remove one event counter.
When a "Fenrir" creature you or your opponent controls leaves exile, remove one event counter.
When there are no event counters left on this
card, destroy all permanents.