The "Heart of the Brotherhood" was a First Civilization artifact that was used to activate the Prophecy Disk, taking the appearance of an oval locket, which could be opened to reveal a small portrait of Jeanne.
During the early 18th century, the medallion was in the possession of the Assassin Brotherhood on Saint Domingue. The artifact was stolen by the African slave Jeanne, who had previously turned down an offer to join the Brotherhood. Jeanne was soon sold to the Louisianan noble, Philippe de Grandpré, and took the artifact with her to New Orleans.
Jeanne became her owner's placée and sired a daughter, Aveline. After Philippe's new wife Madeleine de L'Isle informed Jeanne that François Mackandal was seen boarding a ship bound for Louisiana, Jeanne employed Madeleine's aid and left New Orleans to flee to Chichen Itza in Mexico. Jeanne left the Heart with her daughter Aveline, who was unaware of its true nature.
Jeanne later found fragments of the Prophecy Disk during excavations of First Civilization ruins in Chichen Itza, but hid them so that they would not be found. Aveline, who became an Assassin, journeyed to Chichen Itza twice and found both halves of the disk and took them back to New Orleans. After using the Heart to activate it, Aveline witnessed a holographic recording of Eve's election as the leader of the human rebellion against the First Civilization.