Elder Thing

The Elder Things were a fictional species created by H. P. Lovecraft.

By the 25th century, fringe archaeologists like Bendecker, Vildson and Urnst believed they were real. Twelve million years before the 20th century, a Celestis fictional generator used At the Mountains of Madness to bring the Elder Things and their city into existence in Antarctica. A group of Time Lords from the War's future, not knowing the Elder Things' true nature, were regenerated to resemble them. They killed the creatures, then took their place, thinking they were blending in. They set up a base in the city as part of their plan to free the Fendahl for use against the enemy. (PROSE: The Taking of Planet 5)

Biology
The body of an Elder Thing was an upright ribbed cylinder and quintilaterally symmetrical, like a starfish. It had a five-pointed-star-like head. It had ten tentacles, five used as arms and five as legs, as well as black wings resembling a bat's. They communicated via microwaves. (PROSE: The Taking of Planet 5)

Behind the scenes
The Elder Things appeared in H.P. Lovecraft's 1936 novel.