TELL ME… WHAT DO YOU SEE?
Very little is known about the No-God, save that he utterly lacks remorse or compassion and possesses terrible power, including the ability to control Sranc, Bashrag, and Wracu as extensions of his own will. Because of his armor, the so-called Carapace, which eyewitnesses describe as an iron (or nimil) sarcophagus suspended in the heart of a mountainous whirlwind, it is not even known whether he is a creature of flesh or of spirit. According to Mandate scholars, the Inchoroi worship him as their savior, as do — according to some — the Scylvendi.
Somehow, his mere existence is antithetical to human life: during the entirety of the Apocalypse, not one infant drew breath — all were stillborn. He is apparently immune to sorcery (according to legend, eleven Chorae are embedded in the Carapace). The Heron Spear is the only known weapon that can harm him.
The No-God was killed by Anaxophus V at the Second Battle of Mengedda in 2155. According to popular legend, his body turned to ash, which swept across the land and caused the Indigo Plague. Mandate scholars dispute this, claiming that the No-God’s body was recovered by the Consult and interred in Golgotterath.
Known as Mog-Pharau (from which “No-God” is derived) in ancient Kûniüric. Known as Tsurumah (“Hated One”) in ancient Kyranean. Known as Lokung (“Dead-God”) to the Scylvendi. Known as Mursiris (“Wicked North”) to the Shiradi. Known as Cara-Sincurimoi (“Angel of Endless Hunger”) by the Nonmen. Known as Great Ruiner to the surviving tribes of Men in the Ancient North. Known as World-Breaker.
No-God is invisible from the outside, therefore the Gods cannot see him and help their believers against him.
Author explained in Q/A: A better way to think of the No-God is as a philosophical zombie (p-zombie), of a piece with all the other soulless instruments of the Inchoroi. A perfectly unconscious god, and so in that respect, entirely at one with material reality, continuous with it, and so an agency invisible to the Outside.
In The Unholy Consult
During the final moments of the battle for Golgotterath, the No-God was summoned. Once again before Golgotterath in 4132, all across the world, humans could feel his presence. Babies were again stillborn. His resurrection caused the Great Ordeal to scatter in panic, therefore beginning the Second Apocalypse. The Hordes swarmed around him, and the remaining armies of Anasûrimbor Kellhus were destroyed. 
- The Warrior-Prophet, Chapter 7
- Encyclopedic Glossary, ‘No-God’
- Encyclopedic Glossary, ‘Battle of Mengedda, the Second’
- Encyclopedic Glossary, ‘Indigo Plague’
- The Warrior-Prophet, Chapter 1
- Encyclopedic Glossary, ‘Tsurumah’
- Encyclopedic Glossary, ‘Lokung’
- Encyclopedic Glossary, ‘Mursiris’
- Encyclopedic Glossary, ‘Cara-Sincurimoi’
- Encyclopedic Glossary, ‘Great Ruiner’
- Encyclopedic Glossary, ‘World-Breaker’
- The Unholy Consult, Chapter 20