Creature: Rathis
"They are twisted creatures of the planes beyond, aye. Many-armed and many-eyed, carrying a disturbing crown and raising the dead like no other. But they don't become normal zombies, like in any haunted graveyard between here and the Sixth Ring, no. They become coiling, bizarre, green-skinned beasts, as if a normal person traveled to that thing's rotting birthplace and returned with the same fold in reality in themselves as that thing spawned from."
Eldritch sentries. Rathis are hulking, twisted creatures from the Outer Planes that spawn seemingly with no reason and no purpose. Their existence is a simple convergence of chance, a rip within reality that is torn by the winds of misfortune, out of which a rathis climbs like pus from a wound. They are strange creatures, their limbs and faces reminiscent of humanoids but their minds completely other. Their green-blue skin represent more of a sac or membrane that contains the writhing, coiling mass of their muscles. Pierce the skin of a rathis with magic, and it will seem almost distraught.
Raise their servants. Rathis, despite being largely purposeless and fatherless, have a tendency to seek out dead creatures, from which it creates a new being: the rathis abomination. Humanoid corpses that spawn abominations no longer look like the person that they once were, but become four-armed, stretched husks that look and act like the rathis and are connected to it like a hive-mind. The rathis is the king, the nexus that connects its abominable servants, and that orders them around. Any rathis found wandering has a large chance of having collected a trail of abominations that wander along with it, protecting the rathis and, upon death, being raised by it over and over again.
Aberrant intelligence. Despite the rathis' wholly alien mind, it can be reasoned with. Many rathis have needs and wants that are beyond humanoid capability to understand or meet, but a rathis that is left alone, or provided with anything that seems to please it (from more corpses to raise to food that it doesn't consume, to powerful magical items or simple rubbish in some cases) will still not fight or protect anything that doesn't interest it, but it can be passed by without conflict. The difficult part in making a deal with a rathis is figuring out what it wants, if anything.
Aberrant nature. A rathis or rathis abomination doesn't require air, food, water or sleep.
Friends and companions. Rathis are rarely found around any other aberration aside from its own abominations. A rathis that spawns in a civilized area may surround itself with as many abominations as it can, or with any sort of humanoid minion it can find in its area. Rathis are fiery fighters against creatures that breach their territories or pose any threat to the rathis or its "companions", and many rathis that don't yet have any abominations seek out conflict to turn the bodies of its fallen enemies into its quiet, abhorrent convoys.
Under the Read more, you'll find the stat block for the Rathis Abomination.