There’s a plethora of builds to explore in Warhammer 40K: Rogue Trader, and if you’re the type who enjoys having a trusty animal (or animal-equivalent) companion by their side, then the Overseer Archetype has exactly what you need. This archetype, which was added in the Lex Imperialis DLC, is all about pets, and unlike the Cherub and Servo Skull, these are much more practical.
Familiars may seem weak at first, but once you invest enough love into them, they can become killing machines that complement many builds in Rogue Trader. Here are all the Overseer pets you can use in-game.

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Cyber-Mastiff
Cyber-Mastiffs are the iconic hunting hounds of the Adeptus Arbites. They can run around the battlefield without triggering attacks of opportunities, and they ignore their target’s blocks as well, making them excellent hunters.
If you’re looking for a well-rounded companion, or if you simply want to sic a mechanized attack dog at enemies, then this is the familiar for you. Cyber-Mastiffs are designed to work together with your character, and if you can take advantage of its abilities, you’ll be able to clear even the hardest of encounters without breaking a sweat.
Cyber-Eagle
While not as imposing as a chromed-up attack dog with the bite force of an industrial trash compactor, the Cyber-Eagle is still as lethal. and they’re great Familiars for Officers. Players can order this metal menace to rend enemies with its talons or create tactical opportunities, either by gouging a target’s eyes out or baiting them to accidentally shoot their teammates — the latter makes this Familiar extremely effective at dealing with snipers.
The Cyber-Eagle is all about tying up priority targets like bosses and other hard-hitting enemies, and since it’s always in someone’s face, you can expect it to draw a lot of attention. They also tend to take a lot of damage due to the nature of their abilities.
Servo Skull Swarm
Unlike the cyber-animals above, the Servo Skull Swarm is all about buffing allies and debuffing enemies. It has the ability to echo non-Psyker support abilities, causing them to affect more than one target at a time. This includes support abilities that allow squadmates to perform extra turns, such as Bring It Down.
Apart from extrapolating support skills, Servo Skull Swarms also provide a variety of other effects that are perfect for battlefield control, such as the ability to make enemies attack each other, force enemies to attack the swarm instead of companions, and restore wounds for allies, making them invaluable for messy fights.
Psyber-Raven
The Psyber-Raven is a support-oriented Familiar for Psykers. Similar to the Servo Skull Swarm, it can relay non-damaging, single-target Psyker abilities to all targets in an area, greatly increasing the value you get from them. This relay ability works on buffs for teammates and debuffs for enemies.
Players can relay offensive Psyker abilities through the Psyber-Raven once they use its Overcharge ability from the Overseer archetype. This turns the raven into a devastating conduit of Warp magic that can debilitate and destroy big groups of enemies.