Greyshire Glacial Grotto is a dungeon in Final Fantasy XV and visiting it is part of the game's main quest in Chapter 3. It is an ice cavern hidden behind a waterfall west of Lestallum. The player can fight a Midgardsormr on the grounds outside it.
After hearing rumors of a Royal Tomb being located nearby behind a waterfall, Prince Noctis's party heads out to investigate. They find there is an ice cavern behind the waterfall and scale its depths until they come to a locked door. Noctis has a key for it, and inside they find a Royal Tomb and Noctis retrieves another of his Royal Arms.
- The player can travel to this location and retrieve the Royal Arm before talking Talcott Hester. If so, he will tell them about the water and the party will tell Talcott they already retrieved it.