Possessed (Chaos Space Marines)
Possessed are daemon-possessed Chaos Space Marines. Vicious warriors infused with the powers of Chaos, the first Possessed Chaos Space Marines were members of the Word Bearers during the Horus Heresy.
Many Marines have allowed themselves to be possessed to show their devotion to their Chaos God or to gain the unearthly power that only daemonic possession can bring. The majority of the time, a possessed retains control over his actions, the daemon never permanently displacing the mortal mind of the Marine. It is only during times of bloodshed and battle that the daemon comes to dominate the pairing, assuming complete control over the shared body. The Marine, already a savage warrior, becomes an utterly relentless and bestial destroyer. His body no longer feels pain. The daemon given free reign, mutates the Marine's human form further into daemonic and inhuman shapes.[Needs Citation]
It is worthy of note that the Possessed are involved in a disproportionately large number of atrocities involving the Ecclesiarchy. Some suggest that so powerful is the devotion of the Possessed to the Ruinous Powers, that their anger is focused on those most likely to speak against their foul gods.
Specialising in close combat due to their bestial nature, Possessed forgo any form of ranged weaponry and rely solely on the Daemonic Gifts provided by the possessing warp entity. These abilities can vary depending on the particular daemon and host body, but they usually take on a horrific daemonic visage, along with various rending claws and talons capable of tearing through flesh and armour alike. They can sometimes even sprout extra limbs, dragon-like wings or gain the ability to breathe fire. 
Notable Possessed Chaos Space Marines
- 1: Codex: Chaos Space Marines (3rd Edition, 2nd Codex), [Needs Citation]
- 2: Codex: Chaos Space Marines (3rd Edition, 1st Codex), [Needs Citation]
- 3: Codex: Chaos Space Marines (4th Edition), pg. 29
- 4: Index Chaotica - Possessed