Ogryns (Homo sapiens gigantus) are a huge and physically powerful Abhuman mutant subspecies of humans, often employed as shock troopers in the Imperial Guard by the Imperium of Man. Ogryns possess many traits prized by the Imperium; they are brutally strong and completely loyal, although extremely limited intellectually, which limits their battlefield role to simple and direct assaults. They come from cold and barren planets in the galaxy with high gravity, such as Anark Zeta, which is why they appear larger, heavier and bulkier compared to baseline humans. An Ogryn's speech is much the same as an Ork's. As you can imagine the combination of brute strength, loyalty and lack of intelligence ogryns possess makes them ideal as body guards for some successful gang leaders and guilders. Necromundian ogryn body guards are usually armed like their military brethren with the Ripper Gun.
The Ogryns are the toughest and largest soldiers commonly used by the regiments of the Imperial Guard. Originating from cold, barren, high-gravity prison planets settled many millennia before the founding of the Imperium of Man, the Ogryns' distant ancestors were once normal humans during the Dark Age of Technology. Thousands of years in the harsh terrains and brutal living conditions of their prison worlds after the start of the Age of Strife caused the fall of the first interstellar civilisation of Mankind, forced their ancestors' bodies to adapt to their hostile environment. Many ogryns travelled to Necromunda with Guard armies and were de-mobed and had to find other employment, many were brought over to do heavy labor in the factories. For what ever reason some ogryns will always be willing to lend their more violent services to some one who is prepared to do their thinking for them.
Almost all Imperial Guard Officers will surround themselves with top-notch subalterns, soldiers,aids, and even cannon fodder to take bullets for them. A prime example is the Ogryn Bodyguard. What better being then an Ogryn to stand next to on the battlefield and make a bigger target? Occasionally these Ogryn will flee or gain their freedom and venture forth into the void on their own. Those that travel to Necromunda learn that they are shunned and will find that their services will gladly be paid for handsomely in the vile Underhive.
The adaptation to the high-gravity environment described above is the reason for the Ogryns' thick skin, powerfully muscular build and resulting monstrous size. Though their adaptations led them to increase in physical size and strength, the Ogryns' intelligence declined to below average human levels. As the planetary conditions (barren, cold, harsh worlds with little food and long periods of starvation) that caused their mutation required only primitive survival instincts, part of their adaptation involved the loss of the ability for more complex intellectual thought since philosophical matters were unnecessary in an environment marked by starvation and a constant fight for life. Ogryns are said to be even less intelligent than some Orks. However, the truth is that their intellects did not actually devolve, but became much more focused on matters such as survival. Ogryns Suffer from claustrophobia which can cause problems in some areas of the hive.
The Tithes Chamber Notaries, sub. Planetary Census (Abhuman) is a sub-division of the Adeptus Administratum that oversees the classification and recognition of stable Abhuman strains within the Imperium. Of these, forty-six types are now listed as extinct, and no records have been received of a further twelve strains for over a generation, suggesting that they too have died out or been assimilated back into the general population of mankind. The status of the remaining fifteen Abhuman races is quite varied and there is permanent disagreement about their specific classification amongst the Adepts of the Tithes Chamber Notaries. The most noteworthy and contentious matter concerning the Adepts is the Ogryn matrix of Abhuman strains. This complex group is currently officially listed as seven distinct types (Alpha, Theta, Type IV, Type VIIA, H.S. gigantus gigantus, H.S. gigantus cranopus and the mysterious Grey Ogryns), but many in the Chamber doubt that these are all separate subspecies, and yet another official revision of the classification is therefore pending -- in a few standard decades.