The monolith lies on the edge of the territory claimed by the Necron Sautekh Dynasty. The identity of its sinister architects is believed to be known to the keepers of the Library Sanctus on Terra. The Eldar maintain a Webway portal close to the Monolith, denoting its location with the same rune used to mark the location of the Hadex Anomaly.
The Monolith's true nature became clear in the aftermath of the Great Rift's creation, during the Thirteenth Black Crusade, as it began to glow when the growing Warpstorm known as Cerberax neared its location. This caused a perfect sphere of order untouched by Cerberax's progress across the stars; causing the Tech Priests of Mars' Holy Requisitioners to discover the Monolith was in fact a Necron phase node of immense potency. This was later proved to be true, when the Necron ships of the Sautekh Dynasty arrived to defend the Ymga Monolith and began to clash with Daemons of Khorne, that had emerged from the Cerberax Warpstorm. This conflict has become known as the Cerberax Wars and the Ymga Monolith plays an important part for the Dynasty's forces as visions from the Imperium's Corinthe Mind-Scryers, show that the Monolith is somehow physically duplicating every Necron ship, that makes contact with it.
- 1: Codex: Tyranids (2nd Edition), pg. 37
- 2: Warhammer 40,000 4th Edition Rulebook, pg. 91
- 3: Warhammer 40,000 5th Edition Rulebook, pg. 117
- 4: Codex: Necrons (7th Edition), pg. 13
- 5: Warhammer 40,000 3rd Edition Rulebook, pg. 278
- 6: Codex: Harlequins (7th Edition), pg. 11
- 7: Gathering Storm: Fracture of Biel-Tan, Chapter 1: The Dance of Destiny - Addenda Inquisitoria
- 8: Fabius Bile: Clonelord (Novel), Chapter 18