"Supposedly thrown into the sea by a prince of the dissolved Holy Roman Empire in the early 19th century."
Using the clues in the treasure rumor titled "Treasure Vault Rumor" in their notebook, the player should find the Imperial Treasure in the Treasure Vault in Ciceros Strait's Valka Castle. In order to access the Vault, the player should dive with Oceana and ask her to go through the hole in the door in order to unlock it from the other side, as she is small enough to be able to do so.
The reward for finding this item is thirteen thousand and five-hundred pelagos. Nancy Young also gifts the player the Titanium Gloves, a piece of diving equipment.