Heart of Cthulhu

The Heart of Cthulhu was an artifact tied to Cthulhu, enabling the one who wore it to gain the greatest of the Great Old Ones, while altering their appearance, and putting a massive strain on them caused by the influence of Cthulhu.

To defeat the invaders from the Dark Dimension, Black Widow asked Doctor Strange for a solution. Strange proposed to go and use the Heart of Cthulhu. Despite Strange's and Sif's warnings, Black Widow proceeded and went into the Cthulhu Temple, where she found the Heart, along with cultists of Cthulhu setting up a nursery for the spawn of Cthulhu.

After using the Heart of Cthulhu, Black Widow struggled with the influence of Cthulhu, while Strange asked the Heart back, as part of his duties as Sorcerer Supreme.^[1]