Necrotic Portal

When Necrotic Portal enters the battlefield, exile
each opponent's graveyard. If a card or token
would be put into an opponent's graveyard from
anywhere, exile it instead. Treat cards exiled with
Necrotic Portal as though they were in your graveyard (You may activate abilities of those cards
that can be activated from the graveyard. You may
cast those spells if they could be cast from the
graveyard. Spells that target cards in your graveyard
can target those cards.).