Shriek

The Shrieks are an extra-dimensional species.

Biology
The Shrieks were a nucleogenic lifeforms from another dimension that were capable of gaining access to the our continuum via creating of interspatial fissures. The Shrieks were only able to survive outside their own realm for short periods of time before they were forced to retreat back through the fissure. Their molecular structures were capable of storing a great deal of a form of energy which can be used to drastically augment a vessel's warp propulsion system.

Background
The USS Equinox learned of the existence of these creatures after being stranded in the Delta Quadrant. Short on supplies and moral the Starfleet personnel were helped by the Ankari who before blessing the crew's journey home. Upon witnessing the creatures emerge, the Equinox crew discovered that the Shrieks were emitting high levels of antimatter. Interested in this the crew subsequently constructed a multiphasic chamber to confine the lifeforms for the purpose of study. However they inadvertently killed the creature, but from the corpse they learned that the nucleogenic energy stored within could be used to enhance their warp core to speed their journey home. Using this augment their warp engine they could ttravel over ten thousand light years in less than two weeks. However, the energy extracted from a single lifeform could only increase their warp factor by 0.03% for a single month, thus the crew began to systematically lure and murder more of the lifeforms. These actions did not go unnoticed by the Shrieks or the Ankari, the former began to attack Equinox repeatedly until the arrival of the USS Voyager. While the crew of the Equinox kept their sister ship i the dark of their questionable actions, it was later revealed when the Equinox chose to attempt to destroy Voyager and kidnap two of their crew mates. Learning the full story of what they did, Captain Janeway angered at this betrayal to the ideals of Starfleet relentlessly pursued the rogue ship. Reaching out to the Ankari to act as intermediaries to speak with their alien benefactors Janeway promised the Shrieks that they would be allowed to destroy the Equinox to end these crimes, but until she captured the crew of the Equinox to stand trial for their actions.

Culture
The Shrieks were a benevolent species who held a special connection to the Ankari, a species native to the Delta Quadrant, who regarded the lifeforms as "spirits of good fortune" calling them from their realm to bless their journeys.

Appearances

 * Star Trek Voyager: Season 5: Episode 26: Equinox
 * Star Trek Voyager: Season 5: Episode 27: Equinox II