Mini Map location of Treasure Hunt #20
Collect your reward
Magic-Powered Locator: Level 3
Trigger[]
In Disc 4 talk to Virno in Virno's Tavern on Uhra's Main Street.
Treasure Location[]
Hint: Valuable materials lie on the seabed near Crater Island
Location: You'll see the red dot south-east of the island Grand Staff was on (see screenshot).
You can do this hunt even when before the second visit to Grand Staff.