Oceanspire's Mistake is a special Heart of the Sea recovered during the confrontation with the King of Oceanspire.
Role in the story
The relic is needed during Nora's Quest. When players receive the Heart, it carries unsettling evidence that the Hollow's effects persisted after the kingdom was transformed.
Obtaining
Defeat the King as part of Nora's investigation and claim the story reward. Players who have already received the Heart do not repeatedly receive another story copy from the encounter.