Vagran
Vagrans were "a race of s" who were formerly native to the planet Vagra II. The species, as a whole, departed the planet "a very long time" prior to the 24th century.

The Vagrans were said to have "perfected a means of bringing to the surface all that was evil and negative within," so that they would free their "bonds of destructiveness." 

As these emotions came to to the surface, it formed into an entity, a "second skin, dank and vile" – a "skin of evil" identified only as Armus. What remained was then discarded on Vagra II, left alone and rejected by those who created it, where it suffered for eternity, festering in its own anger.

Those that departed Vagra II were later described by Armus as "creatures whose beauty now dazzles all who see them." ()

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Species
Memory Alpha articles named from supplementary resources