An unknown group, the Nullmind follows groups like the Heartless and the Nobodies, in that it's name is an opposite of what it's members are. In that Heartless are hearts given form, and Nobodies are beings without hearts, the Nullmind are minds given shape.
As with the previous groups, strong Nullmind retain a humanoid form, while lesser ones have more bestial, and unusual form, serving as soldiers, while the stronger ones serve as leaders.
The head leader of the Nullmind is called Zenams, and as like the previous groups, is an aspect of Ansem/Xemnas/Xehanort. Like his previous aspects, he to is obsessed with obtaining Kingdom Hearts, believing with it's power, he can rejoin with his other aspects, then use the power of Kingdom Hearts and become all powerful.
Like any leader, Zenams too has soldiers, here are a few of them.

This is a higher Nullmind. While the lesser ones tend to have more bestial, and creature like forms, the higher ones retain their humanoid form. While they are only few in number, they are leauges above the lessers, as far as power goes. Being humanoid, and retaining their intelligence, they are wildly unpredictable, both in actions and abilities. While Zenams is the leader, or general of the Nullmind, the other higher Nullmind could be called his Colonel's.

This is a Hollow, and is the Nullmind version of the Shadow's and the Dusk's. They move by gliding along the ground, and attack by charging it's enemy.

The Morhand is a stronger enemy, made more difficult to defeat by the fact that it's eye needs to be hit to hurt it. It moves around by walking on it's fingers, rearing back and exposing it's eye before it attacks. It attacks by lunging to grab it's enemy, squeezing it's enemy, thereby hurting and also restricting the movement of it's target.

The Shadow Streak is an aerial enemy, usually flying around out of reach of melee strikes. It's main attack involves the heart shaped object held by it's claws, which is actually a bomb it drops on it's targets. As soon as the bomb explodes, another appears in it's claws.

The Greuber appears like a relatively harmless enemy, as it's round shape and knee high height don't give it much of a menacing appearance. It's waddling walk doesn't help it much either. What actually helps it however, are the blasts of wind it can fire from it's mouth, which can be dangerous. From launching it's target some distance away, or into some wall, tree trunk, or the like, to also gathering and firing small projectiles within the wind it launches.

The Lithozan is a more difficult adversary, due to the fact that part of it's body is solid rock, the other part being plasma. It lies in wait for a victim to come past it, usually being ignored for the pile of rocks it looks like, at rest. It's when it's victim passes, that it awakens, and takes it's usual form. Being part rock, it has incredible strength, as well as being hard to take down. The plasma holding it together also adds in it's attacks. There are two types, which can be told apart by the color of the plasma, red or blue, with the red adding burning heat to it's attacks, and the blue adding freezing cold.

The Draugur seem harmless in appearance at first, resembling a slightly transparent, ghostly being. The danger of it comes from it's appendages, with which it can make solid into scythe like blades and slash with them, extending with them as well, to attack as far away as 10 feet. While physical attacks can hit it, the attacks to very little damage, so it is better to hit it with magic attacks.

The Jiang plant looks harmless, and indeed does nothing but disperse a cloud of spored whenever someone gets close. It's these spores however that make it dangerous, as they can turn people into zombies. Those under control of these spores loose many of their higher functions, such as thought and regular speech, instead "talking" through moans. Attcks are reduced to clumsy slashes and hits with whatever weapon the victim usually used. The victims can be stopped by the usual means of stopping a zombie, removing the head, but they can be "cured" by destroying the plant, which will use it's victims to defend itself.

The Steuern is a very small enemy, only a couple inches high, and very dangerous, able to move quickly and leap rather high. Because of it's small size, it does not attack by regular means, but instead uses others, by leaping onto the back of it's victim's head and digging in with all it's appendages. It then takes control of it's victim, either outright making it fight others, or manipulating it's victim to do actions it wouldn't normally. Those under it's control retain all their abilities and fighting skills. It needs to be forced off by it's victim by either the victim itself, or making the victim unconscious, at which point it can be defeated fairly easily, having little defense or attack abilities without a host.
----------Bosses----------

The Nyctoyong Is a particularly dangerous adversary. There is first the fact that it is a dragon, with sharp claws and sharp teeth, but these are not the least of it. A more noticeable ability is that it can pass through solid objects like they are nothing, by traveling through the regular world, and the world of darkness. Managing to exist in both at the same time, it can "blink" in and out of both worlds, giving the illusion of teleportation. One of it's more dangerous attacks is a darkness breath. Instead of breathing fire like you would normally expect a dragon to do, this one breathes darkness. The effects of this attack vary upon the victim however. If the victim is used to the darkness, like Riku was, the attack will do little more then knocking them back. If the victim is one of the light, so to speak, then the attack will be damaging, alternately feeling like being frozen solid, and being lit on fire, with a momentary depressive aftereffect, lasting up to a minute.
That's it for now, and a very big thanks to Huai_Yali, who drew the enemy designs. They actually came first. Also thanks to ladyAnlu for drawing the images for the higher Nullmind.