Yagghorth

The yagghorth are a strange type of lifeform, originally thought to be a spaceborne animal but later found to have a unique intelligence, empathy and telepathy. Yagghorth are considered supremely dangerous to humanoid space travelers, who typically are killed en masse when their living areas are intruded on by the monstrous meat-eaters.

James T. Kirk had studied Federation historical accounts of yagghorth encounters, and was of the belief that they had been named whimsically by an enthusiast in the works of H.P. Lovecraft, although other language historians had found the roots of the name yagghorth in the obscure tongues of other worlds' dark histories as well. Kirk only knew one person who had seen a yagghorth and lived, his friend Maria Kellogg.

The yagghorth is a large, multi-tentacled creature with oily, slimy skin, and a skeletal squid-like head. The creature moves about supported on multiple ambulatory tentacles, which are edged with razor sharp chitin and bone extensions. Yagghorth communicate with each other through small noises like clicks of their chitin and also a rhythmic bobbing dance motion which is created naturally as they adjust their weight across many tentacles. Besides tentacles for support and manipulation, the yagghorth also have smaller retractable tentacles that are used for sensory purposes. Yagghorth conversations can frequently include abrasions and cuts as they will lay their sharp extensions across each others' bodies in an exchange, playfully slapping and nipping with their cutting extensions.

Yagghorth have a unique type of psionic energy manipulation ability, to perform psion jumps. Because the yagghorth mentality can naturally emit mu-spectrum energy, they have developed the ability to remove themselves from space and time and then reinhabit space-time in a different location, provided that there is a mu-spectrum energy field to serve as a medium of exchange. Although this was initially unknown to space travelers, a ship would typically be attacked unexpectedly by yagghorth when traveling near mu-spectrum fields, such as those emitted by Turtledove anomaly points. When an empath or telepath makes contact with a yagghorth, they will find the creature feels like it is "dreaming itself into the new place".

By the 2260s, few members of Starfleet had seen or heard of these creatures, but a select few had survived an encounter or had the unenviable task of recovering a vessel that yagghorth had fed aboard. The yagghorth, hungry for blood and meat, would materialize aboard, and use their tentacles to flay any lifeform near them. Those attempting to escape in any opposite direction would find the yagghorth was able to rematerialize in front of them, or even to jump aboard a separable excape craft. Typically, a recovery vessel could only expect to find a ship with severe internal damage, bloodsoaked walls and gnarled bits of skeletons aboard a victimized ship.

It was documented that most incidents of yagghorth infestation occurred within five parsecs of a Turtledove anomaly point, leading most such phenomena to be declared standing hazards to space travel. In 2269, an escape pod was discovered in Sector 8 with a short video recording of the crew of the USS Harriet Tubman being killed by a yagghorth, a major advancement in Federation knowledge of these beings.

In a possible alternate timeline, a future Federation had learned to enslave the yagghorth as powerful, albeit dangerous, pack animals. The future Federation was directed by a group called the Consilium, and employed all star vessels with a psion jump drive generated by an enslaved yagghorth. In order to keep the yagghorth at bay, the Consiliar masters would have to employ an empath or telepath to serve as the direct keeper of the creature. These empaths and telepaths would be slowly driven insane by the inhuman, dreamlike perspective of the yagghorth psyche, eventually able to communicate with none but the yagghorth. As the empath would be in the direct presence of the yagghorth, they would eventually "converse" with them by performing bobbing dances, and growing their nails unnaturally long to perform stratch play on the yagghorth tentacles, and receive many scars being scratched in return. The use of an onboard yagghorth would also involve grotesque feedings, with replicators programmed to spew blood and meaty gut material in order to convince the yagghorth to remain in the ship's engine areas.

Known yagghorth
In the 26th century's Consilium timeline, Dylan Arios's Nautilus was driven by a yagghorth named Nemo who was partnered with a Vulcan boy named Sharnas and the Consilium ship Savasci was driven by a yagghorth named Khethi partnered with a Romulan woman, Karetha.