Not a horribly difficult task, but a bit of running
Darklight Palace:
Go past Naythox's throne room and to the far back of the palace where the bed chambers are located. In one of the far southern rooms, you'll find Manservant Ryzal. Hail him and follow his dialogue to spawn two "a Darklight gua
I just tried this for the first time. Made the acid wash tried to "cleanse" the BP with it in the forge on the small-bank platform. "Cannot combine these items in this container."
But the same combinel worked in the forge in the nearby blacksmith shop.