Oath of Eldoon

When Oath of Eldoon enters the battlefield, exile target creature until Oath of Eldoon leaves the battlefield.
Whenever a planeswalker you control is dealt
damage by a creature, that creature phases out.
(While it's phased out, it's treated as though it doesn't
exist. It phases in before its controller untaps during
their next untap step.)
"For keeping peace and order, I will keep watch."