In the Second Kizan War, an unsanctioned group of necromancers out of Idril did their part in helping Rúmil, turning captured giants into death giants. Released in the Nemestyxe caverns, the death giants wrecked havoc on the dwarven supply lines moving along the Brother Tunnels.
Though the war has long since passed, death giant numbers have not declined. They now go on their own forays, capturing giants across Iruk and into the Gakhs. In Nemestyxe, they take them to their temples to Thasmudyan where some are given a new existence as a death giant.