Shadow of the Storm

He will give you Silverlight if you've dyed or destroyed it.

Talk to Father Badden at Uzer, east of Shantay Pass. (Optional: take the magic carpet to Uzer)

Pick and grind a black mushroom (the closest is just south-east of the stairs east of Father Badden). Use it to dye Silverlight black. You can find some beside the staircase, downstairs east of the stairwell, or in the north east corner of the room, east of Evil Dave.

Go down the stairs.

If you do not have the strange implement from The Golem quest, you can pick it up from the ground in the northwest room.

Talk to Evil Dave wearing your three black items and your dyed Silverlight. He is standing at the entrance to Agrith Naar's demonic temple in the underground Uzer ruins.

Talk to Denath.

Talk to Jennifer to get a demonic sigil mould.

Talk to Matthew.

Go to any furnace and smelt a demonic sigil.

Your black outfit can be discarded at this point and replaced with combat gear. Keep Silverlight for the duration of the quest.

Talk to the clay golem outside the ruins about last night.

Look in the nearby Broken kilns for a book until you have found the Demonic tome (there's a broken kiln north of the Rug Merchant and one behind the walls east of the staircase that are easy to miss).

Talk to Matthew back in the lair.

Go north to talk to Denath and write down the incantation he tells you.

Complete the circle and click the sigil to chant the incantation. Be sure to remember it, as you’ll need it again later in the quest.

Be sure to take the sigil from the floor, or you will have to make a new one at a furnace.

Enter the portal and take Tanya's sigil.

Tell Evil Dave to return to the lair - you should have 4 sigils now.

Go up the stairs, talk to Father Badden and Father Reen.

Talk to the golem.

Return to the throne room downstairs.

Talk to Matthew to start the incantation.

Form the circle and Chant demonic sigil and say the incantation in reverse. (If you have forgotten the incantation, it can be found on page 6 of the demonic tome.)

Kill the demon with the Silverlight (dyed). After defeating it, you will have the Darklight equipped.

You can damage the demon with any combat style, but you must equip the Silverlight (dyed) as it dies.

Quest complete!