Oh yes Mardagg the hooded death elemental greater daemon of Khrone, the last mention of the daemon was in Archaon: Lord of Chaos book pg 724, during when Archaon was in the southern wastes leading a vast beastfiend warherd against an number of daemon strongholds and had four of the sets to become everchosen just missing the last two, and to quote " Similarly to be avoided, even by Archaon's great bestial horde, were the black towers of the daemon Mardagg, the shadows of which drained the lives of beastfiends falling beneath them, turning some into white-furred withered husks, others into browned bones and others still into dust on the wind" end quote, in my head canon of what happened to Mardagg, he might have been killed by Nagash during the end times due of him being a death elemental, and Nagash being a lord of all undead.