Whispering Depths - The Dark Amethyst and the Phase Spider Matriarch. You won't be able to open the Baldur's Gate 3 Necromancy of Thay just yet. That's because you need to find the Dark Amethyst.

Jump down, and you will land inside the Whispering Depths dungeon. This area is full of webs and phase spiders. Dark Amethyst is present (X: -561, Y: -357) near their nest where the Phase Spider ...

Once you reach this location, the Dark Amethyst will be lying on the ground underneath the nest. You can claim the item by killing the Phase Spider Matriarch in combat or using a Dexterity-based ...