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 E'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 later by the Captain-General once the Emperor wasn't in a position to do it 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 will not leave the Emperor's side unless under a direct order from the Big Guy Himself (Valdor got sent to Prospero, for instance), something that hasn't happened since He was enthroned upon the Golden Toilet after FUCKING HORUS had his little temper tantrum. Their duty is mentally and spiritually exhausting even for a Custodes, and so they are rotated out of service when the Captain-General judges that they have served long enough. Those who served with the Hetaeron Guard are likely to become Aquilan Shields, tasked to protect important individuals in the Imperium.
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. The Emperor was probably a big fan of the man (or was the man himself, for what we know) and thought the Imperium would be cooler with some good old Greek stuff. Funny thing, the feminine greek word for "companions", hetairai (ἑταῖραι), was used to designate top-tier, well-educated prostitutes. Obviously, the Fabstodes approve this.
Hetaeron Guard are actually represented in 30k, being an Elite choice for Talons of the Emperor list. Absolute beasts in close combat, they start at 210 points per 3 models, so they cost 15 points per model more than Custodian Guard, but get some awesome buffs in exchange. They have basic Custodes statline, BUT have 3 wounds, 3 attacks, I5 and Ld10. Also, Counter-Attack USR. THE RAPETRAIN HAS NO BRAKES.
In means of equipment, Hetaeron can exchange their default Guardian Spears for almost any weapon from Custodes arsenal, the only exception being HQ-only Paragon Spear. Your kinky veteran-bananas can get Solarite Power Talons to mince MEQ with S6 AP3 Shred and Master-crafted Specialist Wepaons, Adrasite/Pyrrite Spears, Magisterium Vexilla for some buffs and Paragon Blades for S6 AP2 MURDEROUS STRIKE BLOODBATH AT I5/I6. And if they happen to come across some tanks, it is possible for them to do some RAPE using Solarite Power Gauntlets, which deal S10 AP1 glorious master-crafted I1 DESTRUCTION. And you get bonus attack for 2 CCW, since Gauntlets aren't Specialist. And everyone can get a Praesidium Shield for 10 points. Enjoy your Bananas of Total Annihilation. By the way, don't forget that the whole squad can get Arae-Shrikes(auto-choice), Melta-bombs(pretty useless most of the time because solarite gauntlets) and Teleportation Trasponders(must-have for mass-deepstrike armies, totally free when Valdor is your Warlord).
Current meta suggests bringing squads of Solarite Gauntlets together with Paragon Blades/Shields combo for maximum cheese. It's important to remember that shielded buddies don't get bonus attacks for 2 CCW, so don't give shields to your boxer-bananas. It is recommended to get 2-3 Paragon/Shield Custodes in front and leave 5-6 Boxers behind them. This way you'll get a balanced combo of well-protected AP2 on Initiative, followed by A LOT of S10 AP1 punches. Throw a Tribune or Valdor for maximum carnage. Have fun.
|Forces of the Adeptus Custodes|
|Command:||Companions/Hetaeron - Shield-Captain|
|Troops:|| Allarus Custodians - Aquilon Terminator - Custodian Guard |
Custodian Warden - Sagittarum Guard - Sentinel Guard
Vexilus Praetor - Venatari - Warder
|Walkers:|| Contemptor-Galatus Dreadnought - Telemon Heavy Dreadnought |
Venerable Contemptor Dreadnought
|Transports:||Coronus Grav Carrier - Drop Pod - Grav-Rhino - Rhino|
|Vehicles:|| Caladius Grav-Tank - Dawneagle Jetbike - Gyrfalcon Pattern Jetbike |
Pallas Grav-Attack - Venerable Land Raider
|Flyers:||Ares Gunship - Orion Gunship - Stormbird|
|Titans:||Warlord-Sinister Pattern Battle Psi-Titan|
|Auxiliaries:||Sisters of Silence|