Cache in the Castle is a Side Quest in the game where you join Arthur Plummly (NPC) in a treasure hunt in the castle. Arthur has two treasure maps, one for himself and one for you. He will give you a map with three hints. Read this guide on how to find out where the landmarks in the castle are and where to find the hidden treasure.
Find The First Landmark From Arthur’s Treasure Map
The first landmark can be found in The Astronomy Wing. Just go down the stairs in front of Arthur to find a Rihno skeleton. You just need to pass near it to register this objective.
Find The Second Landmark From Arthur’s Treasure Map
The next landmark is at Transfiguration Courtyard. From the previous location continue walking down the stairs and use exist the building by using the two big doors. This will lead you to the fountain with the dinosaur statue. Just need to pass near to complete the objective.
Find The Third Landmark From Arthur’s Treasure Map
The last landmark is a portrait. Go behind the fountain with the dinosaurs statue and then walk through another set of doors. Go up the stairs until you come across the portrait that is drawn on the treasure map.
Once you have found this portrait, you’ll need to cast the spell Accio on the handle above the portrait. This will reveal a hidden chest behind the portrait.
Mansi