Umbra (Warhammer 40,000)

The Umbra are a species resembling black spheres capable of manipulating darkness around them to their own advantage.

The Umbra are multi-dimensional beings which only resemble blackened spheres due to an inability from observers to mentally comprehend and process their true forms. They can control shadows around them to attack their enemies, solidifying the dark into limb-like blades, teeth and other nightmarish shapes at the Umbra's whim. They have no known homeworld, but instead drift through space and gather around areas resonant of the Warp, such as derelict starships, Warp engines and even entrances into the Webway.

The Umbra share a significant aversion to light, actively avoiding any and all light sources. Light is so harmful to the Umbra, even a standard-issue lasgun of the Imperial Guard can inflict grievous harm to them. Upon death, an Umbra will emit a psychic scream that painfully imprints a series of images in the minds of those in close proximity at the time of its death. These images include a humanoid figure splintering to pieces, a Warp-storm, deep space, then the word "linger."

The Hrud believe the Umbra to be fragments of their god, Qah, he who lingers. Supposedly, Qah was killed by Slaanesh, who scattered his remains across the material universe, leaving them to wander in desperate search of a way back into the Warp and presumably coalesce.