Demons are beings that stem from the Burning Hells, the remains of Tathamet. There are a host of different forms of demons, ranging from weak and animalistic in their intelligence, such as the Fallen, to the incredibly strong and powerful Prime Evils. Demons sprang into existence along with angels, Anu and Tathamet obliterated each other, and are their anti-thesis: angels are beings of light and order while demons embody shadow and chaos. All demons are selfish and opportunistic beings who value their own existence above all else and continuously seek power and dominion over those they deem to be weaker.
There are few common features between demons, as opposed to angels who all share similar features and traits. Demons can be small like Imps or large like Diablo, intelligent like the Great Evils or dumb like Gulag, monstrous like Thonos or seductive like Lilith. Some features seem to be more common than other though.
- Dangerous appendages: Most demons are killing machines and so usually have many claws, talons, spikes or fangs to aid them in killing their enemies.
- Resilience: Unlike humans, demons are very resiliant creatures who can sustain a lot of physical damage before dying.
- Corporeal: Unlike their angelic counterparts, who are described as sound and light, all demons appear to be physical beings.
Many demons also possess dangerous and strangely colored blood.
It is important to note that demons and undead are two different things. The undead are oftentimes used by the forces of Hell in their armies, but there appear to be no undead demons at all. All the undead seen in the games and books were either animals or humans while they lived.
The Burning Hells are ruled over by the Great Evils, first by the Prime Evils and presently by Azmodan. There appear to be no other set ranks in Hell. Powerful demons aspire to usurp the places of those above, all with the intent of receiving the favor of their respective Great Evil. One example is Astrogha who during the Sin War attempted to wrest control of the Triune from Lucion and in so doing strengthen Diablo's support of him.
Only two known demons are known to have actually tried to usurp the place of the Great Evils without being a Great Evil themselves, those are Lilith during the Sin War and Kabraxis from The Black Road. It is uncertain whether the latter is canonical.
 List of Notable Demons
There have been hundreds of various breeds of demons shown in the various games and books, too many to list here. Below follows a list of notable demons instead
There are no other known formal ranks in Hell. All other demons serve the aforementioned Great Evils directly or indirectly through another more powerful demon. We do know of several demons who are factors of power in their own right.
- Assur, leader of a demon army in the short story Demonsbane. Favoured of Diablo, he is near impervious to damage.
- Astrogha, a spiderlike demon serving Diablo. He has a major role in both The Sin War and Moon of the Spider.
- Gulag, a shifting servant of Baal. Appearing of equal status to Astrogha, he was eventually defeated by Uldyssian.
- Lilith, daughter of Mephisto and sister of Lucion. She led demons rebels with her to create Sanctuary before being cast into The Void by Inarius.
- Lucion, son of Mephisto and brother of Lilith. Led the Triune on Sanctuary during the Sin War before being erased from existence by Uldyssian.
- Thonos, a demon summoned by Lilith consisting of tentacles and eyes, which attacks Achilios and Uldyssian, then is killed by Achilios.
- Hephasto, a master smith of Hell who works at the Hellforge. As the Hellforge is the only place where the Soulstones could be destroyed, it is very likely that Hephasto had a high rank within Hell.
- Kabraxis, the main villain in The Black Road. Kabraxis is mentioned to have extreme patience and knowledge and was a threat to the Three.
- Shenk the Overseer, the commanding officer of the Baal's armies laying siege to Mount Arreat during the events of Diablo II: Lord of Destruction.
- Xazax, a powerful demon in the novel Legacy of Blood. He transforms a mortal army into demons, and is personally dealt with by Diablo at the end, which would suggest some form of power if the Lord of Terror bothers to deal with him in person.
|Prime Evils||Baal • Diablo • Mephisto|
|Lesser Evils||Andariel • Azmodan • Belial • Duriel|
|Notable Demons||Assur • Astrogha • Gulag • Thonos • Kabraxis • Lilith • Lucion • Xazax|