The Avatar found the Gems, and after a treatment from Nystul, used them on the big Blackrock Jewel in the sewers, to weaken it and open passages to other worlds. These steps were essential to destroying it in the end.
The Gems were:
- Small round Gem from Tarna.
- Square Gem from Killorn Keep.
- Diamond-shaped Gem from Anodunos
- Large round Gem from Talorus.
- Cylinder Gem from Scintillus Academy.
- Triangular prism Gem from Pits of Carnage.
- Rectangle Gem from Rhiannon.
- Heart-shaped Gem from Ethereal Void.