Easy "A Mad Stash" Achievement
This is an achievement that's obtainable in the Ashes of Malmouth expansion. You can get this achievement during the side quest Mad Ramblings from Ivonda in the Malmouth resistance base in the Steelcap district. For this quest you have to find her notes and bring them back to her. Her notes can be found in the north of the steelcap district and will be displayed with a star. However, once you've obtained the notes, don't bring them back to Ivonda immediately! Instead, you can now find the secret stash yourself! In the southern part of the Steelcap district there's a zone called The Tomb of Herald Mathis. In the beginning of this small dungeon there's a loose torch (it's the only unlit torch in the dungeon). Clicking this torch will open a secret door just south-west of it and in there you can find Ivonda's stash, which will unlock this achievement and possibly some nice loot as well.