Enigma

The Enigma (Limo Malevolus or Malevolent Sludge) was an unclassifiable single-being species first encountered in Messier 64, the Black Eye Galaxy. Without any form of government, or sense of moral, the vicious Enigma reaped the benefit's of it's own galaxy a great many years ago, mercilessly devouring all of it's natural life. It's origins, as well as wether it was a member of a larger species is unknown.

It's encounter with the Niex had immediately sprouted into the Precursor-Enigma War.

Biology
The Enigma featured it's own unique biology. Like a virus, it could be considered a semi-biological non-cellular lifeform. It's complex biology offered it the ability to manifest itself into any form that it had wished, as well as to produce a seemingly infinite supply of it's tractable sludge-like biomass. It was also supplied with an indefinite natural lifespan, or immortality, thus, eliminating the common necessity of reproduction.