Holy Hall or Twilight Temple is an instance dungeon where you fight a series of bosses in order to obtain crafting materials only found from those bosses.
You can craft weapons that are distinct because of their green glow, or armour that is normally a notch above the rest.
A few screenshots of me fighting bosses solo. It takes forever to kill them, but you don't have to share the mats with anyone else, so the profit is tremendous.
