Abhuman

Abhumans are descendants of humans who have physically evolved after being isolated on worlds with various environmental conditions.

In an Imperium where genetic mutation and spiritual corruption are often interrelated, abhumans are a focus of much controversy. In more liberal times under the Emperor, even markedly divergent abhumans such as the Beastmen could serve in the Imperial Guard. Since the Emperor's stasis however, only the lesser deviants, such as Ogryns and Ratlings, are allowed citizenship. However, they are still distrusted by the Puritan members of the Inquisition.

In White Dwarf issue #304, an official article was published featuring Doctrines to allow Imperial Guard armeis to take units of Abhumans, expanding on the Ratling Snipers and Ogryns of the rulebook. The article featured Beastmen (or Homo Sapiens Variatus), Mutant Slave Levies (ordinary mutant slaves rounded up for cannon fodder), Feral Ogryns (even nastier and more primitive than regular Ogryns), Nightsiders (originating from worlds of perpetual or near-perpetual darkness, little to no ability to see but perfect warriors for Night Fighting missions), Afriel Strain Soldiers (genetically engineered from DNA taken from great heroes of the Imperium, very unlucky and unpopular), Subs (relatively genetically stable but still hideously deformed mutant sub-breeds) and Gland Warriors (Imperial Guardsmen implanted with special organs and glands that secrete combat-useful chemicals, such as stimms and pain-killers).

Beastmen
Beastmen are horned, hoofed, hairy abhumans. They were formerly recruited for the Imperial Guard, where they used their bloodlust to fight for the Emperor and atone for the sin of being born mutants. They were led by individuals called packmasters. Beastmen are no longer seen in Imperial service; no doubt elements of the Inquisition convinced the Administratum that they couldn't be so radically altered from normal humans without being tainted by Chaos.

Ogryns
Ogryns evolved on high-gravity, low-temperature prison planets. They are huge and stupid but extremely loyal once introduced to the Imperial Cult. It's even said that those who fought as rebels in the Horus Heresy only did so because their superior officers lied to them about which side they were on. Ogryns are used as shock troops, wielding heavy automatic shotguns called ripper guns, which are also weighted to be used as clubs. They tend to be claustrophobic and thus are difficult to transport in Chimera APCs. They are led by "Bone'eads," who have undergone Biochemical Ogryn Neural Enhancement so they're not quite so stupid.

Ratlings
Ratlings are tiny, hairy-footed abhumans who serve as snipers in the Imperial Guard, although this role is becoming less popular now that pure human special weapon and light infantry squads are fielding marksmen as well. Ratlings also serve as cooks, a skill they no doubt learned in order to feed their own stomachs. They also tend towards kleptomania.

Squats
Squats originated on high-gravity worlds towards the galactic core, making them short and tough. They seceded from the Imperium during the Age of Apostasy. They are said to have been mostly been wiped out by the Tyranids. The race is an equivalent of the fantasy dwarf.