Silver Sword (Superior): Under The Elverum Lighthouse

This diagram is located under the Elverum Lighthouse on the very southern tip of Ard Skellig. Journey there by trail or boat, and locate the entrance to a cave on the hillside above the rugged shoreline

Locate the wolf sign at the cave mouth to aid in mapping where the treasure chest is, before entering the cave and then exploring the winding tunnels within. Keep exploring until you cross an old elven bridge, down some steps to a tomb. The chest is behind the tomb with another chest.