Slayer of Hades

King of the Underworld:
When Slayer of Hades enters the battlefield, the battlefield changes to the Underworld, while the battlefield is the Underworld, you control all undead.
Yautja Prime:
When another Yautja enters the battlefield, gain +1/+1.
Additional creature type: Planeswalker
As long as the battlefield is the Underworld, Slayer of Hades is also a Planeswalker.

"A Yautja once ventured into Hade's realm, he found many worth prey amongst the Underworld."