In Game Description
This ancient ring, engraved with a large green flower, is of unknown origin.
Hastens the regeneration of stamina.
Treasure from a corpse in The Great Hollow
When you are going down the tree root at the beginning, staying on the first root, there's a hollow tree on your right. Drop into the hollow tree to land on the platform containing the corpse - (video)
Increases rate of stamina regeneration by about 20 per second (~45% more than base) when equipped.