Exploration is the most important part of Baldur's Gate 3, and that's why you really need to investigate every corner of the game's world if you don't want to miss valuable loot. If you have happened to reach Underdark, then you probably know that this brutal place is home to many big little secrets, treasures, and creatures.
Upon your exploration in Underdark, you may have come across an area named Grymforge. There is so much going on in this part of the Underdark, and you can put an end to multiple quests. Aside from that, there are some major treasures and loots in Grymforge, including Harper Stash, that you may not want to miss out on them.
How To Get To Grymforge
If you are already in Grymforge, you may skip this part, but for those who don't know, the path to Grymforge requires you to sail in the dark with a boat. To do so, you need to head to the southwest of Myconid Colony in Underdark. On your way, you will face Duerger forces. Based on your pact with the Myconids, you may kill them all or talk your way through. At the foot of the Duergar outpost, you will find a boat. Board it and sail in the dark.
Another boat will interrupt you in the middle of the path. You can either convince them you are friendly or enter a battle with them. Either way, you will eventually find yourself in Grymforge.
How To Find The Harper Stash
Before we start giving you direction, make sure you have at least one lockpick tool in your inventory. The Harper Stash is located in a tricky place. Firstly, you need to get to the location where Nere is trapped inside. So, once you get off the boat, turn right and head upstairs. Follow the next set of stairs to the top of the castle until you reach a hall with some lava around it.
Here, you will spot a door blocked by loads of rocks, but next to it, there is an open gate. Go through the gate, turn right, and climb up the cliffs. Now you should be able to see a campfire, in front of which there is a staircase leading down. Follow the path, and you will see another staircase that leads to a Cragged Rock wall. Climb down the wall and interact with the big chest on the edge of the giant cliff.
As soon as you interact with it, the chest will turn into a monster, spawning two more friends as well. You need to kill all of these monsters. If you have any attack or magic capable of pushing the target like Force Tunnel, you can easily make these monsters fall off the cliff and die instantly.
Once you are done killing the monsters, create a manual save and head to the edge of the cliff, and you will get an Investigation prompt. If it's successful, the Harper Stash will appear in front of you. This stash is not unlocked by default, and you need to use your lockpick tool.
Keep in mind that the stash requires you to roll 20 to unlock it. So, make sure that you add all bonuses you have. If you fail all your attempts, you can load your manual save to try it again.