The Omni-King is a very small humanoid figure. He has a rather blank expression on his face and has purple and blue stripes on his face as well. He also has no nose present. He wears a pink vest on his body and on the front has two "omni" kanjis (全) present. His head has a rather lemon like shape, with his two ears being pointed and grey.
His first appearance is at the end of episode 40 in Dragon Ball Super.
Zenou (全王) is the entity that stands above all of the 12 universes. Beerus explaned him as the god above all gods.
Zenou does not fight, however he has the ability to erase. We see this in episode 67 when Goku summons him to Earth hoping he could erase Fused Zamas.