The King

Appearance
The king usually wears a white suit, except for one time when he wore a black suit for azuma. He also wears a mask with black big eyes and kind of dog-looking ears.How he looks underneath was never really shown but you could see that he had darker hair in chin-length. He usually is big and thin.

Human Form
He actually looks always like his usual appearance.

World Devil Form
In his world devil form he wears a black suit and has striped devil horns.It also seems like he has longer ears.

Personality
He is a psychopath who does what he does for fun. Because he enjoys despair he kills many people and doesn't care which world will be destroyed. He likes to play with his "toys" and imitates voices for example or lies.He is unpredictable and because of the many feelings he has inside he sometimes acts weird.

Past
In his past he was born to become the king and the darkness itself. Its not 100% clear but it were probably the old Cheshire Devils who wanted to get a monster as a king. He had the power to read the citizens mind and could feel everything happening in the tower. Because many bad things happened there such as killing, sadness and despair he had to feel the same as a baby and as he grew.It's like he felt the darkness of 100 million people. He had to endure it until he really became the darkness itself, that's when the Cheshire devils thought of him as a success and wanted him to save maze. But after he declined to promise them he said he doesn't even have a darkness of his own. He killed one of them which was the bloodlust of another one, he cut himself which was the will of someone else as well. So the Cheshire Devils thought of him as a failure now. The king realised that while he killed someone and cutting himself he felt something like joy and so he decided to fight for maze to have the possibilty to do as he wants and have fun.

At the end
In the end he thought he had lost but after realising that being alone in a world of nothing is the greatest despair he were really happy.