People Without Personhood
The world of Iocrade, at least within the sphere of the Gods, is made up of something called Immaterial Matter - material unmade, the raw stuff of the Faewyld purchased by the Iocrade Gods for concessions to the Fae Gods, pseudo-matter shaped into reality via raw will. If the Gods were to ever cease to govern these materials, it would eventually disassociate, disperse, and disintegrate. However, there are times when raw Immaterial Matter makes its way into our world. When this occurs, it will eventually begin to disintegrate as well - and when it does, it is possible that a colony of Australis Men is born.
Most Australis Men will die before they even have much of a chance to live - they experience gravity inversed, and those who don't materialize indoors will likely just float up into space until they are destroyed by suffocation. However, these rare beings are dreaded by dungeoneers, for fear that they lurk crawling on the ceiling. Known for their dreadful ability to steal the personality, the self, from their victims, many consider such an experience a fate worse than death - left comatose as the being who left them to die masquerades as them.
The average Australis Man, if such a thing can be said to exist, is humanoid, with a head, torso, two arms and two legs. However, that basic and flexible constraint is the only standard one can expect - Australis Men have fluid shapes, and are often multicolored with shifting shades running up and down their body, and with misplaced faces on their bodies and the sides of their heads. Stronger Australis Men tend to be more complex. Their appearance is often compared to imagery from an intense psychedelic hallucination.
Australis Men experience inverse gravity, and when prowling in ambush can be observed crawling on ceilings to keep from being seen early. They often have long arms for bashing and grasping at their victims. Their facial expressions do not change as long as they are in their Nascent State, and remain stiff and neutral. Australis Men are followed by what appears to be a vapor, but is in actuality the energetic release of residual Immaterial matter dissipating on their body. An Australis Man that has lived long enough will eventually cease to release the alleged vapor. Pieces removed from an Australis Man will dissipate into similar vapor, as will the corpses of the deceased.
In the even that an Australis Man fully seizes a being's ego, their appearance will significantly stabilize, showing a single face and maintaining a consistent color scheme. Their faces, at that point, will also begin to be used to make facial expressions like a human being. They are likely to maintain certain surreal visual elements, however, if they have any to begin with, at this point.
Australis Men do not have to eat, sleep, or breathe, but undergo a decompression event when in a vacuum, killing them quickly. Nevertheless, Australis Men are ambush predators for their power of Personality Parasitism. Australis Men are born in colonies of 2-5 on average, the result of Immaterial Matter dissipating in the Material Plane. Larger sums of Immaterial Matter can result in larger colonies, and stronger Australis Men. Roughly 9 out of 10 colonies are lost to the inverse gravity, and float up into space where they decompress and die. However, those that materialize underground or indoors - more likely than one might think, because while colony formation is likely to be close to the point of dissipation but can occur from as many as 100 kilometers away - can remain in wait for years.
Mindless, Australis Men have a very simple instinctive strategy - crawl up over the target, strike them and grab their head, and apply their power to absorb their ego and personality. They do not need to grab the head, but it is the most likely part of the body to be within reach, so the easiest target in most cases. This will be repeated until such a time as the Australis Man has absorbed the sum total of a person's personality, at which point the victim will enter a comatose state, no longer possessing a sense of self. An approximation of that person's personality, divorced from their experiences and memories, will thus be born in the Australis Man, who will develop an intelligence and become, functionally, a person.
Australis Men, even those that are intelligent, have no sex drive, no sex organs, and are incapable of sexual reproduction. Most Australis Men will not attempt to raise or create a child, but those who's personality included a strong parental desire will likely begin to research the Immaterial Matter, to attempt to induce a dissipation-based birth of new Australis Men. Australis Men do not attack one another, even the intelligent ones. If one were to be somehow convinced to do so, they would undergo a collapse back into the Immaterial Matter that made them, alongside their colonies. Australis Men do not age, and are biologically immortal.
Obviously, being rendered comatose in a dungeon is a major danger, as is having one's personality stolen and eroded given that force of personality can be very important to effectively use certain skills and powers. Bringing light and always checking the ceiling is vital to avoid their dangers. If struck by an Australis Man, one should immediately avoid or break the grip they will then attempt to make. Polearms or ranged weapons will not be needed, as they have human-length arms and will certainly be in range of your weapons if they can hit you.
In the event that Personality Parasitism occurs, the victim or their allies are advised to kill the perpetrator as soon as possible, as this will return the stolen personality back to the victim instantly. This is true whether or not the victim is rendered comatose. If a victim is fully drained, they can partially recover with magical assistance. However, part of their essence was taken - the Australis Man responsible must be killed to return it.
Furthermore, even if one is not grappled or drained, one must fear the strength of the Australis Men, who will recklessly assault the victim and beat them haphazardly in an attempt to grab them. Some particularly slippery adventurers managed to avoid being grappled so long that they simply were beaten to death instead. This may prevent Personality Parasitism, but presents a whole new problem - that the victim is dead, of course.