Ymnog, also called Ymnog the First Titan, was a Godbeast, the Grandfather of Gargants and the zodiacal sire of the World-Titan Behemat.
He was one of the primeval gods of the Realm of Azyr.
The footstep-shaped craters found across Ghur, known as "Ymnog's Trample," were left behind as he traversed the Realm of Beasts in the Age of Myth.
Age of Myth
According to legend Ymnog was even more vast than his son, Behemat, said to be so large his club shattered reality into land, sea, and sky.
He was slain by Sigmar during the Age of Myth using the Great Bolts.
Age of Sigmar
During the Realmgate Wars of the Age of Sigmar, Archaon planned to use this information about Ymnog's death as part of his efforts to corrupt Behemat, the son of the First Titan.