Kethuru, the Mighty is one of the Soulless and fought alongside Illith at the onset of the Elder Wars. Despite being a formidable foe throughout the Elder Wars and later the Vernal Wars, Kethuru's power would not be fully realized until the final days of the Vernal Gods, when He was the final remaining Soulless, filled with the essence of many of the Elder Gods as well as the Vernal Gods and the mortal races. Its amorphous body began to bloat and expand, blanketing the entire globe of Lusternia and covering every inch of the land with His viscous, suffocating skin.
In Their final act, the Vernal Gods each sacrificed Their own power to form Avechna, the Avenger. Avechna's magick, bolstered by the strength of the last nine remaining Vernal Gods, successfully imprisoned Kethuru out of phase with the Prime Material Plane, trapped behind the Living Seals.