Alzilu Alwahsh(the boogeyman)
The shadow realm has its own physical manifestation of darkness. It's original names were, the beast of darkness, the shadow beast, or, its very first name ever, Alzilu Alwahsh(shadow beast in Arabic). However, this being is most commonly known as the boogeyman, despite the fact that it refers to itself by the name of Alzilu Alwash. This, Alzilu, is a creature of incredible power. It's just unfortunate that this being's entire purpose for existing is to bring chaos and bad dreams. It's very literally, a manifestation of fears and nightmares. It is often considered a 'master of the mind' and if it were to enter your mind, you would most likely either be petrified beyond comprehension, or you would be lucky enough to die.
While in the shadow realm Alzilu can only influence dreams, but when he is summoned, he enters the mindscape, which is technically in the real world, but he can't change reality without a physical body. As long as Alzilu is in the mindscape, he can enter the minds of any living creature. He will remain in the mindscape as long as he isn't properly sent back. If he is properly sent back, he will no longer be able to occupy the mindscape, and he will go back to influencing bad dreams, rather than tormenting people in their minds.
Alzilu's powers are such that if it were ever to enter the real world with a physical form, it could very well shift all of reality into a living nightmare. Alzilu is an 'it' because very technically, it does not have gender, but interestingly enough, it seems to prefer taking on a more masculine appearance, and by that I mean that it refers to itself with male pronouns, has a very 'manly' sounding voice, and mostly takes the physical appearance of a male. This is odd because you would expect a being of chaos to not be too particular about those sorts of things, let alone actually put forth effort to make an avatar with a specific gender. I guess even beings of pure chaos have personalities! In fact, Alzilu has a very sick and twisted sense of humor. He find playing with reality, and tormenting people as being funny. The number one thing you can never do is doubt his creativity.
While Alzilu can shape shift, and does so often, he also tends to show himself in a specific form. This form isn't actually the body of any living creature, and that's because it's a random hodgepodge of different animal body parts. This favorite form of his consists of the body of a dragon, the back legs of a horse, the head of a lion with two long front fangs, the enlarged antlers of a deer, the wings of an eagle, a long naked whip like tail with a large fluffy tuft of fur at the end, and the front legs of bear, but with long retractile claws and an opposable thumb. Please note that these body parts may vary in size depending on what kind of animal it originated from. He himself is usually three or four times the size of a fully grown dragon.
Even though Alzilu's body is made up of many different animals, they all seem to be made of the same material, and by that I mean his body looks like it's made of some mixture of black ink and slimy sticky tar. His skin is constantly crawling or moving around like the waves of the sea, if the sea were incredibly thick and slimy. The only parts of his body that aren't that way is the dragon crest on his back, his deer antlers, his fur, and his wings. His dragon crest and deer antlers are black and shiny like stuhrling metal. His fur and wings are dry looking and covered in soot and grime. His description is something that is only known due to those who have seen him in their dreams. Although most who dream about him don't remember him, only that they had a terrible nightmare, but those who do were so terrified by his appearance that it haunts them forever. Dreamcatchers can keep him away, but he only influences bad dreams, he is not the only cause of them. In fact, most nightmares are caused by inner feelings or emotions rather than being caused by Alzilu.