Cursed Relics Quest

Name: Cursed Relics Quest.
Location: The Castle.
Requirements: Completed first mission in The Castle Quest by killing Executioner Arranz just to push the lever.
Reward: Green Tome, an Explorer Brooch, 30 Piece of Gray Ancient Stones, Grey Tome and 25 Piece of Blue Ancient Stones.

If we do not have access to the castle's underground yet, perform The Castle Quest by killing Executioner Arranz, and if we already have access, follow the map to the lever:

If we managed to get to the lever and open the wall, follow the map below.