Stormheart

Stormheart is a Legendary one-handed Dagger. The item is named after the "fictional" weapon in the Excerpt from Daila's Diary.

This item also has a level 94 Mythical version that is found in Lokarr's Secret Quest.

Aquisition
Stormheart is not part of regular loot tables and cannot drop from monsters. It drops once per character on Ultimate difficulty only, after completing the Daila's Diary side quest. It is located inside the Tomb of Korvaak,  within an Ancient Urn. (Note that the urn can sometimes be broken by enemies.)

The Mythical version is found in an Ancient Urn in the Desolate Wastes if you are doing Lokarr's Secret Quest.

Finding the Dagger enables Daila's Secret Quest. Talking to Daila Thornsbury after finding Stormheart enables several new minor dialogue options.