Haask was a worm-like abomination with a gargantuan mouth filled with countless rows of teeth. Its skin was a poisonous green covered in red sores, with veins and organs somewhat visible beneath. Haask survived as a symbiont attached to the outside of Hargut's body.
Haask, a monstrous greathorn minotaur, conquered Ironfang Keep in -981 DR, declaring himself priest-king of the land of Grong-Haap. He ruled Grong-Haap for six hundred years, expanding it to include the modern lands of Thar, the eastern Moonsea, and northern highlands of the Vast.
In the Year of Craven Words (-350 DR), Haask summoned an elder evil to combat a goblinoid horde: Hargut of the Gray Pestilence. Hargut slew tens of thousands, consigning their souls to the Barrens of Doom and Despair, but three humans, the mortals who would become known as Bane, Myrkul, and Bhaal, took advantage of the distraction to attack and nearly slay Haask, revealing his true form as a doppelganger of the elder batrachi race.
As Haask lay dying, the Dead Three persuaded him to agree to a ritual that would bind him and Hargut together as one entity under the command of the three adventurers. Hargut agreed, and together they became Haask, Voice of Hargut, a fell entity bound to Ironfang Keep and responsible for the creation of numerous abominations and chimerical monstrosities during the centuries that followed.