Editing Warhammer 40,000/7th Edition Tactics/Adeptus Custodes (section)

===Battle Brothers===
*'''Adepta Sororitas:''' They have Immolators and come with shit tons of Melta and flamers. Also can bring warm bodies with 3+ armor saves.
*'''Adeptus Mechanicus:''' They bring loads of ranged firepower, while you guys provide a solid anchor and beatstick. Also take the Vexilla to ensure your slow-moving gunline never retreats! That is really all that there is to say about Skitarii or the Cult Mechanicus.
*'''Astra Telepathica:''' Ally them in.  Seriously, ally them in.  25 points gets you the ability to re-roll your reserves and when you have the ability to Deep Strike your entire army you do not want to get fucked over by a bad reserve roll.  Primaris Psykers with Biomancy can also greatly help the unit as they can make it harder to kill with Endurance, restore Wounds to the unit with Life Leech, hold their own with Iron Arm/Warp Speed/Smite, weaken enemies with Enfeeble (in case you wanted to ID Marines with your S6 dudes) and act as a Warp Battery for more useful Psykers if they end up rolling Haemorrhage.
*'''Space Marines:''' If you're taking Custodes in a Marines army, it's because they wished their Terminators/Command Squad was as good as you. That, or you needed to borrow their Spartan Assault Tanks/Stormravens.
**'''Grey Knights:''' Can work with Draigo since one of the Custodes' weak points is their low mobility barring Deep Strike and Draigo's fixed power of Gate of Infinity will overcome that. Or you could just buy the Venerable Land Raider, since Draigo is only 40 points less anyway.
**'''Blood Angels:''' Sanguinary priest can make these already tough bastards unstoppable, especially as they have eternal warrior. Quickening (imagine 8 s6 ap2 i8 attacks) and Unleash rage can also be really helpful. 
*'''Imperial Guard:''' They bring the cheap warm bodies to hold objectives, and lots of ranged goodies like the Leman Russ tank and Basilisk artillery. The only thing they cannot give you is Assault Vehicles.
*'''Imperial Knights:''' Custodes don't bring much to the baby titans that they couldn't already do, but the baby titans do put out rapid-fire ordnance and AP3 miniguns. 
*'''Inquisition:''' Oh hell yes. Henchmen squads of Acolytes provide the bodies, Mystics and servo-skulls help you in case you wanted to Deep Strike your Custodes into battle. Also, the Custodes make the best bodyguards to an Inquisitor of any kind. The Hereticus Inquisitor can straight-up shut down psychic attacks with the Null-rod, and the Ordo Xenos Inquisitor can help you guys with Rad Grenades to weaken the enemy, and Psychotroke grenades to fuck with the enemy and help you out tonnes. The Ordo Malleus Inquisitor in Terminator Armor will probably blend in the most with you guys. Also if you care, this maybe the fluffyist option; if the Adeptus Custodes goes to war in the 41st Millennium, only the Inquisition's gonna know about it.
**Do note that the Inquition's Null Rod is one of the best ways to deal with Psychic shenanigans (especially if you didn't get the right Warlord Trait, or have multiple units that are vulnerable).  Sure the Inquisitor with it will cost the same as another Custodes, but if you use the Inquisitorial Representative Detachment you can gain another Warlord Trait out of it too, and the immunity to mind fuckery's well worth it.  Maybe you'll get lucky and manage to get Master of Ambush, thus bypassing all of the Custodes' mobility issues.
*'''Sisters of Silence:''' Golden armored anti-Psyker girls with Golden armored Glory boys. These girls give you anti-Psyker protection while you give the beatstick to them. Nearly vital if you don't have the right Warlord Trait and are up against Psykers while not allying in any of your own.
*'''Also:''' one thing to note is it is possible to form a Combined arms detatchment with the custodes with the use of Greyfax, Cawl or Celestine.