Exotic Methods

To finish this quest you need to have a master herbalist.

After given the mission enter the herbalism screen to craft a potion.

You'll see "Dwarven Regicide Antidote"

You will need: 4 Elf Root 2 Life Stone 1 Flask 2 Concentrator Agent

Once you have made the antidote speak with the Dwarf that gave you the quest and give him the potion.