Enoulian
The Enoulian are a xenos species that populate the the Calixis Sector, though experts suggest they might come from the Halo Stars. They shine for their above than average hatred for the Imperium and Humanity.
Biology
Most enoulians are described as being humanoid beings, around 1.5 meters of high and not really muscular. Their faces have little to no special traits, being mostly featurless (no eyelashes, no facial hair, no nose...). Their eyes are slanted and simplistic, with being just pupils with a vertical shape. Their nostrils are not protected by a nose or something similar, it basically being two vertical slits on their face. Their body secretes an oily substance that both gives them a yellow-green colour and makes them ungrabbable. Indeed it is said that they lack most forms of friction on their bodies, which makes us wonder how can they even grab stuff with their hands. They communicate with themselves with grunts and whishpers, but they are able to talk Low Gothic if needed, albeit a very rough one.
The Enoulian and Mankind
The enoulians were one of the many, many xenos species that Humanity steamrolled during the Great Crusade and beyond. Experts believe their homeworlds were destroyed during one of the Legion's campaigns throughout the galaxy, and that has generated on the enoulians a deep hatred for the Imperium. Indeed, it is said that an enoulian only needs the sight of an imperial aquila to enter REEEEEE mode and go on a murder spree of humans. Fights between the enoulians and imperial forces show their advanced technology (though not nearly as advanced as many other elusive xenos species), mostly crystal based knives and guns.
Another thing of interest is that they use as a trade unit things such as bodies, bones and other similar stuff. This has made many Ordo Xenos' experts believe that their hatred for Humanity is making them slowly fall to Chaos, and they may use those things to fuel dark rituals. So you can imagine this puts their extermination in a very high priority.