Once inside this dungeon, you'll be immediatly confronted with a huge cathedral full of monsters, as well as a boss in the center. Clear out all of the monsters as much as possible before engaging the ghost boss in the center, because once you kill him, the real challenge of this dungeon will appear. Attacking the final boss will draw any monster left alive to its defense, so clear out as much as you can before making your attack.
The final boss - Lilith - has two forms. The form is her human form, and shell attack the tank throughout the duration of this part of the battle. When enough damage has been dealt, Lilith will transform into a huge bug monster, and increase the ferocity of her attacks. She'll star to AoE the group at this point, so make sure the healer is on point. Killing Lilith ends this dungeon in victory.