The Adeptus Custodes are the personal bodyguards of the Emperor. They are roughly similar to the Space Marines in that they are superhumans implanted with genetically-engineered organs. Unlike the space marines, they do not get a gene-seed from any Primarch, but instead are custom-tailored by the Emperor himself. They are taller, stronger, and hardier than space marines, and use specialized wargear. They maintain a rigorous training program known as the Blood Games, where selected Custodes attempt to break into the Imperial Palace, while the other Custodes must try to stop them.
Custodes who served directly under the Emperor when he was alive were known as the Companions. While not an official rank, they are respected as being among the few alive who remember him and knew his will.
After the fall of the Emperor, the Custodes have never left the Imperial Palace. They wear black as a sign to show their mourning, and only allow a select few to have an audience with the Emperor. They remain largely aloof of the state of the Imperium, save for times when Terra is directly threatened.
Many of the Custodes have become insane and have stripped off their armor. A few are based on old first edition Warhammer art (some of which appear in episodes 11 and 27), but most are based on various characters from JoJo's Bizarre Adventure, particularly the Fabulous Custodes. Those who have not are still somewhat nutty after all their time spent in isolation, such as the passive-aggressive Emissaries Imperatus, or the Shadowkeepers who consider wearing black as being equally erogenous as being naked.
- Prior to Warhammer 40,000 8th edition, the Custodes were inplayable and were hardly fleshed out past their initial appearance in 1st edition. Besides the part about “shedding their warhead” taken literally in TTS, the show didn’t have much information to go on, including the name of the current Captain-General in the forty-first millenium. This had lead to a couple inconsistencies with canon due to retcons, but are generally played for laughs.