Located inside castle. The route to the right once you enter castle. Not the route that takes you into the coliseum arena. It's the room where all the special weapons, armor, helmet are locked up. You must have all pieces as shown on map. Make sure you have those items on, click on tomb on right side and be prepared for awesome cut scene and one of the best items that you can acquire. I won't say so it doesn't spoil it for you, but it is one of the blacked out items you can't normally acquire. Awesome item is all I can say, very powerful.