Demon Slayer Achievement
Found and killed the ancient demon, Hybris.
This is missable. The scrolls for this quest can only be collected in Act III. You must collect the three scrolls and complete the respective aspect quests:
Wounded Coast: If entering the Wounded Coast from the main entrance, head down the dead end to the South of the entrance to find the scroll. Return to the main path and continue south. The path eventually turns and begins running east to west. Continue along and take your second right. As you head down this branch, you will be attacked by multiple groups of Corpses and finally Medan. After killing Medan, the quest will be completed.
Sundermount #1: Found on the path leading from the Sundermount’s entrance to the Dalish elf camp. After collecting the scroll, pass through the Dalish camp and take the right at the fork by Keeper Marethari. As you proceed up the hillside, you will come to a campfire and be attacked by a large group of shades and an Arcane Horror. Defeat them to complete the quest.
Sundermount #2: Directly behind (North) this campfire where you were attacked is a wall. You will find the final scroll behind this wall. Continue up the mountain and enter the cavern. Exit the cavern through the Mountain Graveyard exit and take a right to continue up the mountain. Pass the loot-able graves and altar and you will be attacked by the demons Gifre, Bysmor and Beacon. Defeating them will complete this final scroll quest.
After finding the three scrolls and completing their associated quests, you will unlock the journal entry for "Awiergan Scrolls: Pride Unbound". You must now head to the Hidden Dungeon in Darktown. If you toggle labels, it is marked on the map as Hidden Lair. It can be found in the northeast part of town, south of Ander's clinic. If you are looking at the change party station outside of Ander's clinic, turn around and the entrance is the tilted ladder by the lantern.