Sun Gem

Sun Gem is a quest item needed in the ruined temple in the Ruined Temple (area). It's needed to remove the shadow walls blocking the entrance to the areas of the dungeon. They can be acquired by solving the riddles in the temple. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition.

In-game description
"This round and polished stone glows with a fierce light and seems to dispel the shadows around you."