Costlemark Tower

Costlemark Tower is an optional dungeon in Final Fantasy 15 and is considered the final and most difficult Royal Arms dungeon.

Contrary to it's implicative name, one must decent into the towers basement levels rather than climb as one would assume. You may only enter the dungeon upon nightfall, upon entering you will begin to descend immediately. As the party decent into the dungeon they will be met with a variety of considerably strong foes as such this dungeon should only be attempted above level 55.