Belega Corridor Chest 2
When you first get to the third floor, keep right to find another staircase to another room upstairs. There’s a chest with a Damascus Vest.
Belega Corridor Chest 3 + 4
Use a hidden passage on the third floor (see the lines connecting the two rooms the arrow is pointing out below). You’ll find a Witch’s Earring and an Aquamarine.
Belega Corridor Chest 5 + 6
Look out for a secret passage while passing through this room in the south part of the third floor. You’ll find amazing equipment that can be purified to be even better later: Guard’s Chausses and Imp-Ending Pike, the ladder which you should definitely give to your current Knight for the boss battle ahead.