Tahm Kench, River King

When Tahm Kench, River King enters the battlefield
exile the top four cards of each
opponent's graveyard under it.
{t}Return a card exiled under Tahm Kench to
its owner's graveyard: Tahm Kench, deals damage
equal to the card's converted mana cost
to any target
"It is my mouth into which all travels end."