In Dragonborn we get to meet Ash Spawns, molten flaming zombies that are scattered in and around morrowind when red mountain mysteriously erupted. I think these ash spawns are creations of Dagoth Ur since ash creatures are usually related to him like ash priest, ash slave, ash ampires, ash storms etc. Or these ash spawns could be the angry spirits of the Sixth House members but i still think Dagoth Ur is involved in some way.
My life for the dark god Dagoth Ur!!!!! show the sissy Alduin and Miraak how real badasses do things!