Found and killed the ancient demon, Hybris.

For this reward, you will need to find three scrolls that lead you to the demon. Once you find the three scrolls, you need to do their vague quest and then head for the demon. The first scroll is in Sundermount. Enter and head for the Dalish camp and the scroll will be on the left of the main path. Continue past the camp and up the right path to encounter an Arcane Horror and a load of Shades. Kill them to complete the first quest and to find a second scroll behind a wall there.

Continue up the path and through the mountain graveyard to the far reaches of Sundermount to encounter more corpses and more named Arcane Horrors. The third scroll is on the Wounded Coast. When you enter from the map, take the first branching left to the dead end and the scroll will be there. Continue along the main path on the Wounded Coast and you will encounter a ton of corpses and an Arcane Horror called Medan. Take them down to complete the third quest. Once all three are done, head to Darktown and just south of Anders location. On the left wall will be a ladder in the corner that leads to the hidden lair. Enter and fight Hybris and his swarm of Shades and Rage demons.