It can be used on a special platform in the Forgotten Vale to open a portal to a cave in Darkfall Grotto. The treasure chest is directly to the right on the platform. If the Dragonborn jumps down into the river and reaches the northeastern bank before being swept away by the current, they will encounter a group of Feral Falmer and one chaurus hunter fledgling patrolling the area.
There are several falmer tents in the cave, and most have chests with random loot. Following the paths up the side of the cave, the Dragonborn will find dead falmer and at the end of the path will find a levelled chest between two clusters of glowing mushrooms.
- Found on the corpses of Frost Giants after killing them in the Forgotten Vale.
- After travelling to, or finding the Wayshrine of Learning (activated by Prelate Celegriath), head towards the northernmost tip of the (unfrozen) lake. On one side of the lake you should see a steep path that will take you up and over a hill towards the next Wayshrine. Opposite this path, on the other side of the unfrozen lake, will be a clearing. The Giant that roams it holds the Amethyst Paragon.