Daemons

Officially identified as 'Demons' by The Republic, these beings are one of the first conscious alien beings humanity had encountered, most eminently during The Lexian Uprising within the Lunar colonies during the closing months of The Second Genexian Invasion upon The Moon.

History
The emergence of these creatures were followed by many attempts of making a formalized classification, most of which had been unsuccessful as theories created were immediately disproven by the newest observations of Daemonic Incursions that routinely occured after their first sighting in The Second Genexian Invasion. Years forward an MIT post-doctorate graduate in xenology, Forrest Mech released an book that conjectured Daemons could not by any means be fitted inside a traditional taxonomic tree and presented the inability for even cutting edge neural networks to come up with a valid theory which could describe existing observations with the possible future ones.

A few hours later a scientific paper was released after it's peer-reviewing was complete, authored by the same individual, Forrest Mech, named The Theory of Daemonic Taxonomy, which described his theory and methodology to separate all Daemonic entities or creatures into seven kingdoms, which were then subdivided into many more categories afterwards. Hundreds of other theories created after his article were also able to explain short-term observations of these creatures, his however had been already adopted by many allocations as it was the easiest to compute against available data. The theory went on to stay valid for two centuries, before modifications had to be done which replaced it with The Modern Theory of Daemonic Classification, that stemmed from the idea that Daemons should be classified depending on their abilities and patronage, rather than physiology as their origins were proven to be either astral or psychic.