The Cursed Medallion is a key item in Kingdom Hearts II. One of 882 cursed Aztec coins delivered by the Aztecs to Hernán Cortés, it curses anyone who has removed a piece from the stone chest to become an invulnerable ghoul until all of the coins, along with the blood of everyone who has ever removed a piece from the stone chest, are returned to their chest. Port Royal's representative Keyblade, Follow the Wind, features a medallion as the keychain.
The curse cannot affect those not native to The Caribbean; so, Sora, Donald and Goofy are exempt from the rules.
Kingdom Hearts II
During the first visit to Port Royal, Elizabeth Swann is kidnapped by Captain Barbossa because she had a medallion in her possession and claimed that her last name was "Turner". After rescuing her, it turns out that medallion was originally William Turner's that she stole because she thought he was a pirate and would be killed. In order to defeat Barbossa, Jack Sparrow, after stealing a medallion to become invincible, and Will have to shed their own blood and return their medallions to the Aztec Chest.
The second visit starts with a fight against cursed pirate, which has Sora and company thinking someone stole a medallion. Jack claims he did not steal it, and Elizabeth rushes to tell them that Will went to check on the Aztec Chest, but he has not returned.
While on the way to the Isla de la Muerta, Jack, Sora, and company meet Luxord, a member of Organization XIII, who has taken the chest from the island. After a fight with the Grim Reaper Heartless, Luxord admits defeat but takes and throws four medallions to Gambler Nobodies. The Grim Reaper then reappears and casts Jack, Sora and co. onto the empty Interceptor which is then blown up by Luxord with the Black Pearl's cannons. Upon waking up, the group finds themselves in a Ship Graveyard and Jack has been cursed. Jack claims that they must find the four medallions and then return them to the chest for the curse to be lifted. The medallions are in all the different areas of the world and are carried by the Nobodies.
After finding all four, the group heads toward the town and finds the Grim Reaper and the Aztec chest there. The boss battle that follows requires Sora to collect all the medallions that are missing from the chest. Once they are all there, the group can finally damage the Grim Reaper. However, the Grim Reaper can steal the medallions from the chest or the ones that Sora is carrying. The only way to make the Grim Reaper drop medallions is to use magic against it. After the fight, Jack drops the chest into the ocean to ensure that the medallions will no longer be a problem.
The 882 medallions first appeared in the Disney film Pirates of the Caribbean: The Curse of the Black Pearl. The film elaborates that in the early 16th century, the Aztecs delivered the medallions to Hernán Cortés to satisfy his greed. However, the coins merely fueled Cortés's greed, so the heathen gods cursed the medallions to forever curse anyone who removed the gold until they return the coins and shed their blood on them. Hector Barbossa located the chest on Isla de Muerta, where he and his crew were all cursed. While they learned how to remove the curse, one of his men, Bootstrap Bill Turner, sent his medallion to his son, Will, but was sent to Davy Jones's Locker as punishment. Ever since, Barbossa and his crew have been seeking Bootstrap Bill's bloodline to finish removing the curse.
Thirteen years later, Barbossa's men track down the medallion at Port Royal, where Elizabeth Swann has kept it for herself. She claims herself to be of the Turner bloodline, and is thus abducted. To save her, Will pursues her with the help of Captain Jack Sparrow, and their adventures lead them to a final showdown on Isla de Muerta, culminating with Will and Jack shedding their blood to end the curse. Following Barbossa's death, his pet monkey, also named Jack, ends up taking a medallion for himself and becomes cursed once more across the rest of the franchise.