"No one can truly command the loyalty and obedience of a hundred thousand howling creatures from the nether realms, but I can... inspire them. And I will accomplish magnificent things."
The Daemon Legions are a playable faction in the game The 9th Age: Fantasy Battle. They are the armies of the seven Dark Gods and Father Chaos, daemons from the Immortal Realm who come to earth either naturally or by summoning.
In the Second Age, a huge golden statue erected by the Eastern Dwarves is said to have been possessed by a daemon of Sugulag known simply as The Gilded Giant. The daemon brought a legion with it, who raided the dwarves of their gold. 
The creation of the Inferno, at the end of the Seventh Age, let loose many daemons upon the Augea and Vetia. One force was lead by Foloy, who attacked the ogres. He drove them them back to the Sky Mountains before being defeated by Tsanas.
The daemon legions reside in the Immortal Realm, many daemons found in the region known as Hell. They are not normally found in the Mortal Realm and cannot remain there unless sustained by magic. 
In places where the Veil is thin, the Daemon Legions are said to be able to push through at will. Supposedly, daemons can be found in some places in the mortal realm however, such as the Wasteland and the Shattered Sea. Presumably because the Veil is permanently thinned in these regions.
Daemons can also be summoned to the mortal realm, through certain rituals and the sacrifice of sentient creatures. To summon a legion, mass sacrifice is said to be necessary. 
Father Chaos is said to be the absolute ruler of the Daemon Legions. Many daemons are believed to serve him directly. Others serve one of the seven Dark Gods, who in turn serve the father. This relationship has been likened with water. Each individual daemon is a stream, flowing into that of a more powerful daemon, which in turn flows into one of seven rivers, finally ending in the ocean of the father. 
The hierarchical society of the daemons appear to be a inherit part of their nature. More powerful daemons can supposedly compel lesser daemons to do their bidding by sheer force of will. 
The armies of the Daemon Legions seem to often by lead by a single greater daemon. Sometimes the daemons in such an army take up traits from this leader. 
Even a small battalion of daemons lead by a greater daemon is said to be extremely deadly. 
The units that make up the armies of the Daemon Legions are the following, sorted by gods:
- Quote by Greater Daemon of Greed (T9A:FB Rulebook, v1.3.5, p28)
- Jorge Zamoran; An account of the peoples, nations and monsters which inhabit the world: Daemon Legions (T9A:FB Rulebook, v1.3.5, p144)
- Urs Bödeker; Banners of the Legions (T9A:FB Daemon Legions, v2.0, p92)
- Explicitus (approx. 1,000 B.S.) Annals (T9A:FB Daemon Legions, v2.0, p68)
- Extract from the ogre epic Tsanas: Lines 3410-3473, translated by Pascaline Caillat (T9A:FB Rulebook, v1.3.5, p86)
- Nazario Calegari (953 A.S.) Circling the Abyss (T9A: Circling the Abyss)
- Verdorben Kantu (784 A.S.) Immortal Beings and Where to Find Them (T9A:FB Rulebook, v1.3.5, p134)
- Georges Sybellicus, extract from The Book of the Infinite Legions (T9A:FB Daemon Legions, v2.0, p10)
- Transcript of proceedings in the Court of Tsuandan, approximately 405 A.S. (T9A:FB Warriors of the Dark Gods, p22)
- Extract from an untitled tome, known to scholars as the Dark Chronicle of the West (T9A:FB Warriors of the Dark Gods, v0.201.0, p28-31)
- Mikhail Psellus, extract from 'On the work of the heretics and their daemonic masters' (T9A:FB Daemon Legions, v2.0, p70)
- Pablo de la Rue, Memoirs (T9A:FB Daemon Legions, v2.0, p28)