I was doing the Telvanni House questline in the council house building in Sadrith Mora and one of the friendly npcs somehow gave me the effect Ring of Toxic Cloud Damage Health 35 and it won't go away, only way to combat it is with TGM.
I have left the cell that the npc afflicted me with this effect but still persists. As it is an enchantment effect I cannot dispel it, nor kill the NPC that gave me the effect as they are essential.
Note: It's the NPC's ring equipped, I do not have it, nor do I have it equipped.