The Resting Place of the Flying Stag

Between the Lighthouse and Widow’s Grotto, on the western coast of Grassy Knoll, are a group of islands. Take a boat or swim across, watching for a boat of bandits, until you chance upon the wreck of the Flying Stag.

Climb aboard this barnacle-bottomed ship, then descend into the waterlogged hull to find a small chest perched at the edge of the water. Pry it open to obtain the following:

Head to safety and open up the mage’s notes, which tell of the sorceror’s attempts to kidnap witcher Kiyan, and take him to the mage’s dwelling. This text seems to place it underneath Temple Isle in Novigrad itself!