Shoggoth

A protoplasmic being, that can form limbs and sensory organs based on need. First created by the Elder Things, millions of years in Earth's past, to be used as servants and slave labor. They developed intelligence and rebelled. They were discovered in the modern era by the Miskatonic Antarctica Expedition of 1930.

A Shoggoth appeared in the Alley directly after the space-time distortion experiment conducted by Allison Flynn opened a portal to its world. There it proceeded to mate with on her way home from the lab.