Those creatures come from another dimension believed to be some kind of afterlife where every "Soul" goes after departing this world, some describe it as a purgatory where they get to wander for hundreds of years before merging with the universal consciousness.
Every now and then some anomalies allow some portals between their dimension and ours to open and let them return and of course, most of them try to escape and go back as soon as possible, problem is that no one told them that if a soul comes back to this dimension, they will lose any kind of form and shape their energy allowed them to have, reducing them to what can only be visibly described as dense smoke, all that is left for them in this state is to find a host in less than three minutes before they vanish into nothingness, it can be any living and breathing being.
If they manage to find and link with someone, their energy will merge with theirs and become one but will still remain as two separate consciousness, once this happens, the invader can still physically manifest as a cloud of dense smoke and take form of a discolored and red eyed version of its host, adopting their anatomy and voice, regardless of what they used to be when still alive. Nevertheless, they can´t be separated much from each other, as being more than 50 meters / 164 Feet away from each other will cause both the host to die and the invader to vanish, meaning that they are stuck with each other until the host dies, and when that happens, they both will return to the other dimension as an unified soul.
When physically manifesting, this beings are able to solidify from the smoke and interact with their environment as any person would do, being able to go turn back into smoke at will, making them have the ability of going either tangible or intangible.
They can project their thoughts into their host´s mind or talk directly to anyone in the proximity if manifesting physically, they are also able to take full control of their body from time to time if their consciousness has enough power to do so, leaving their hosts in their own subconscious while doing so, and at the same time and under the same circumstances, the host is also able to lock them out of their thoughts, which also makes them unable to manifest physically. They also passively absorb the energy of any living being around them and add it to the one that they share with the host, doing it at such a slower rate that it is barely noticeable, but having the option of using this ability consciously, allowing them to absorb it in larger quantities, being able to kill another person entirely just by draining their whole energy.
If they are able to cooperate, they can get to be a force to be reckon with, but since they are actually two different beings with their own memories and personalities, most of the time they are actively fighting against each other, either it being for control over the host´s body or for literally any kind of thing they do not agree on doing. If they manage to cooperate actively, they can reach a point in which their souls will unify without the need of the host´s death, this causes their memories, personalities, and overall their own minds to merge and become one, yet, both of them can now naturally take control of either the physical body or the smoke manifestation, they will still be aware that they are two separate beings but will not be able to tell who is who, suffering from a severe case of dissociation that will eventually go away with time, allowing them to become the same mind with the option of being in two different bodies at the same time, when this happens, one of the eyes of the host´s body will change to red and the opposite eye of the manifestation will turn into whatever eye color the host has.
In this particular picture we have one of those cases, a Blue bird Physician with the ability of mind controlling other people with verbal commands, who suffered an spine injury that requires the constant use of an exoskeleton to not be rendered paraplegic named Katherine Bloom, who on top of her handicap, fell into insanity after experiencing a horrible trauma, yet, she managed to cooperate with her invader, a former scam artist from the 1800´s known as "Melanie" who died in her sleep after a heart attack.
Both of them could represent a serious threat for society, their mind control is dangerous by itself but it gets really dangerous when combined with two unstable, yet, genius minds that take do not normally showcase any regret for their actions when pursuing something they want.
Luckily, Katherine is kind of immature, having a childish behavior at times but being overall kind and good natured, and while Melanie seeks for personal glory, she likes to get her way and having as many people at her side as possible, all of this combined makes them an unstable, chaotic neutral kind of person who tends to look for herself most of the time but is willing to help others in need if able to.
The black latex/oil like material on top of Katherine is actually an experimental compound that allows many types of medical treatment to be applied to the body it is attached to, it works with nanobots and can be used to treat to a certain degree any kind of physical damage and clean, disinfect, and detoxify any kind of hazardous threat to the user such as poisoning, germs, bacteria, among others. Katherine uses it specifically to treat her spine injury.
This latex/oil is a viscous liquid that even when scattered, can reunite itself automatically, attaching, spreading, and creating a layer of a latex like material that sticks tightly to the users body both on the outside and in the inside, entering the body through any cavity it finds. The nanobots inside the compound can be controlled and used with a special application that can be linked to either mobile devices or stationary computers, this led to some people modifying it to be used as a restraining and sometimes as a torture method, nevertheless, some specific sound frequencies are able to tamper with the nanobots behavior, so anyone being forced to wear this compound unwillingly can still be freed if they are somehow able to be exposed to a certain sound frequency.
