Companion

Constantin Valdor. The most famous Companion and Emprah's Secret Lover BLAM! HERESY

Also known as the Hetaeron (from ancient Greek ἑταῖροι, hetairoi, "companions"), the Companions are what most would call as the Emperor's BFF, Friends with Benefits, Big Daddy G's super-secret Princess club. As you may already tell, the Companions are those Custodes privileged enough to stay by the Emperor's side throughout the Great Crusade. There are only 300 of such Companions, each personally hand picked by the Emprah himself and are thus the most skilled and ruthless of the Golden Bananas. While the Custodes themselves are already called the Bodyguards of the Emperor, they only protect the Imperial Palace. The Companions on the other hand are THE BODYGUARDS. No exceptions. You can find these chumps within the heart of the Imperial Palace. The most famous of the Companions is Constantin Valdor who is also a Captain-General to boot and the second closest BFF to the Emperor after Malcador the Sigillite himself.

The Companions never, ever leave the Emperor's side, even after he was enthroned upon the Golden Toilet after FUCKING HORUS had his little temper tantrum. Their duty or protecting the Emperor is so intense it borderlines fanaticism at times. Sometimes being the Emperor's personal maid can be a bit of a bore, however this is not to be underestimated as the Companions must be vigilant at all times in case a certain assassin sneaked in the Imperial Palace itself.

The Companions take orders from no other body in the entirety of the Imperium of Man, there are cases of them refusing to acknowledge direct orders from Lords of the Senatorum who do not sit on the High Thirteen (one case being the Grand Master of the Officio Assassinorum, possibly the deadliest man on Terra) And they can even act against the High Lords of Terra and install new ones if it is within their remit to do so (like helping to depose Goge Vandire and telling Sebastian Thor in no uncertain terms that he would be Ecclesiarch or die) Only the Captain-General being of superior authority. In actuality most of the decisions made in times of conflict is passed down the Shield-Captain whose role is much more flexible and general.

However questions on whether the long isolation has turned some of the Companions into deranged, oiled-up, half-naked, flaming homosexuals is counted by the Imperial Inquisition as one of the darkest and deepest of heresies and is punishable by Rape and then Blamming. Trying to link that to Slaanesh worship is even more heretical and whose punishment is one of the most severe in the entirety of the Imperium. The state of the Companions right now is one of utmost mystery, but what is known is that if the Companions would have ever let their guard down for even a few minutes, then the dark corruption of Chaos itself would seep into the Golden Throne.

As an anecdote, the Companions are a reference to Alexander the Great's elite troops and bodyguards[1]. The Emperor was probably a big fan of the man (or was the man himself, for what we know) and tought the Imperium would be cooler with some good old Greek stuff.