Finding Philomeen’s hiding spot in can be a daunting task, as the exact location is somewhat hidden in a dangerous area. You are not obliged to actually go there, as this is part of an optional side quest, but doing so can result in both assistance during an important mission and rewards. Philomeen is a deep gnome who was able to escape from the cult of the Absolute and is hiding away in the Underdark, near the Grymforge.
Helping Philomeen is one of the possible ways of eventually releasing True Soul Nere in , though not the only one. Regardless, if you are engaging in a righteous-inclined playthrough, you may want to meet the deep gnome and hear what she has to say. Before doing that, however, you will have to find her hiding spot, which may be hinted at after talking to Laridda. The duergar Brithvar also references her, saying a deep gnome fled with smokepowder.
The hiding spot in which Philomeen took cover after stealing the smokepowder is set in the far northwest portion of the Grymforge map in. For reference, it is closer to the waterway through which you arrived rather than the lava-filled portions.
To get there, you will first need to explore the area around the harbor and find a location where two duergar are overlooking several deep gnome bodies. Nearby, there will be a large metal door. After reassuring the duergar about your presence (or killing them), save the game. Then, you must enter the room and head forward, to the far left corner.
You will need to lockpick the entrance to this door, so use a character with high Dexterity, such as Astarion, to succeed at the Sleight of Hand check.
Upon arrival, characters will automatically roll Perception checks and, if successful, you will notice that the wall can be
Read more on screenrant.com