Outsider: Any of the many varieties of monster which serves the Exiled Ones, never from this plane of existence.
Predaten: A hideous Outsider. When needed by an Inquisitum warlock or other member, predaten fasten themselves onto the essence of an Inquisitum humanoid and appear inside them. Then, they burst out of the victim, who is usually instantly killed, and their soul is transformed into another Predaten swarm on their home plane. Once their grisly entrance is complete, Predaten ravege the battlefield, driven only by hunger and the urge to kill. Very few Inquisitum commanders will use Predaten with any degree of regularity.
Mind Horrors: Another Outsider variety, these creatures spawn from nightmares and mad visions.
Mentalis: A feared Outsider creature, roughly humanoid, but physically unimpressive. Mentalis have no true gender, as they reproduce asexually. They can spray a psycho-corporeal gas which has some ability at manipulating thoughts. Mentalis are for some reason weakened by the sight of any holy symbol.
Maravoch: An Outsider variety. Maravoch are gaunt, huge creatures with not a trace of humanity in their appearances. They are roughly insectoid, and have the power to spray bolts of nether energy with a thought.
Ker'Ath: A living weapon form of Outsider, Ker'ath are terifying, exoskeletal creatures whose natural weapons are the equals of many modern blades. They are also very intelligent and individualistic. Among their powers is one to assume a human form, permanently if they so chose. They also have the ability to see through any darkness. Ker'Ath do not feel cuts or suffer wounds from anything short of a silver, magical, or explosive or plasma weapon.
Ancient Terror: An Outsider variety, Ancient Terrors are huge, seemingly lumbering beasts capable of incredible destruction. However, they are not intelligent and often can cause as much damage to the Inquisitum as the foe. Ancient Terrors cannot be exorcised and are extremely difficult to kill.