Rhan-Tegoth

Rhan-Tegoth is a monstrous alien entity; possibly one of the Great Old Ones; who arrived on Earth in prehistoric times and was worshiped in an Alaskan temple, built by pre-human creatures circa three million years ago.

Biology
Rhan-Tegoth a large creature. Squatted down, it still stands almost twice as tall as a human being. Its biological affinities are hard to pinpoint. Although it has been linked to the higher vertebrates, its globular torso is equipped with none less than six sinuous limbs, all terminating in crustacean claws. Its head is shaped like a bubble. It has three fish-like eyes arranged in the form of a triangle; "a distended lateral system analogous to gills"; and a foot-long flexible proboscis.

At first glance, its body appears to be covered in dark fur, but a closer look will reveal that this "fur" actually consists of small tentacles, each equipped with "a mouth suggesting the head of an asp". The tentacles surrounding the beast's proboscis are longer, thicker, and striped, "suggesting the traditional serpent-locks of Medusa". With these numerous mouths, the liquivorous monster pierces the hide of its prey and secretes a digestive acid before sucking out the prey's blood and most of their insides, leaving behind corpses that are both exsanguinated and grotesquely disfigured.

The body of a dog that was sacrificed to Rhan-Tegoth was described as being "flattened, sucked dry of blood, punctured in a thousand places, and wrung into a limp, broken-boned heap of grotesqueness [...] Most of the hair was burned off as by some pungent acid, and the exposed, bloodless skin was riddled by innumerable circular wounds or incisions".

Rhan-Tegoth is a fearsome creature that demands the sacrifice of living victims to it. After eating, it enters a state of dormancy, although it will awake to demand more food later. In the absence of food, it may hibernate for millions of years until some new victim ventures within its temple. It's then implied to brainwash creatures to become its servants and bring more sacrifices to it. These brainwashed servants fancy themselves as priests of the old god, and take it as their mission to feed it.

History
Deciphering clues set in the eight fragment of the legendary Pnakotic Manuscripts, wax sculptor George Rogers and his assistant Orabona discovered the ruins of an old Alaskan temple, dating back three million years, and Rhan-Tegoth itself was sitting on its ivory throne, in a state of complete dormancy, while the bones of its former victims (consisting of all sorts of non-human creatures) laid scattered on the floor. Concealing it from the rest of the expedition, the two managed to smuggle the thing to Rogers' museum in London.

Against the wishes of frightened Orabona, Rogers kept the dormant monster in the museum, and decided to wake it by sacrificing dogs and other animals to it. The monster made Rogers its priest, and Rogers was delighted to serve it.

When Rogers told Stephen Jones about the creature, Jones refused to believe it was real, thinking that the photographs represented another of Rogers' wax sculptures. When he told Rogers that the thing was too disturbing to be exhibited, Rogers' reaction was so maniac and his insistence that the alien was real was so strong that Jones thought the artist had gone mad. To try and placate his anger, Jones made a proposal to spend the night inside the museum to prove that there was no such thing, and Rogers agreed to Jones' condition that, if the night passed without incidents, Rogers would destroy the "sculpture".

That night, Rogers dressed himself in the hide of a Dimensional Shambler (implied to be something he acquired in one of his voyages) and attacked Jones, intending to sacrifice him to Rhan-Tegoth. While the two men struggled, the creature snatched Rogers instead, and Jones managed to run away.

When Jones finally built enough courage to return to the museum, he found that Orabona had mounted what he claimed to have taken for another of his master's unfinished sculptures: the thing that was none other than Rhan-Tegoth, feeding on the unrecognizable remains of Rogers himself.

Appearances

 * "The Horror in the Museum", by (1933)