So the I decided the Dark Halmeryope should have sideburns. That'll make him twice as powerful XoD
But in all seriousness, he controls all dark matter, darkness, etc. The Planet, Livin Pitsa, is made up of the same dark materials that formed Ultimate Evil, as you can see with the landscape.
The Dark Halmeryope can create dark creatures and turn into shadows. He's intangible to anyone but the Light Halmeryope. I'm not specifying any background yet, the public will see that in Krystal later.