The Cursed Blades of Vengeance are sickle shaped blades that cursed anyone who received even the smallest wound from them to be doomed to fatal misfortune.
During feudal days of Japan, the blades were owned by twin sisters. When an evil warlord slayed their family, the sister used the blade to kill him in retaliation and the blades cursed anyone injured by them, to be doom to face death at every opportunity. One night in NYC, a fox-mutant named Alopex, stole them from a museum, intending to use them on her brother Tiger Claw, when Raph and Casey tried to stop her she ended up cursing Casey with the blades. Then she used them to confront Tiger Claw telling him that she was going to decapitate him but she was forced to flee.
When April, Casey and the Turtles confronted her about her vendetta against Tiger Claw and asked to help lift the curse she reveled that the only way to revers the curse was for Casey to use the blades to injure her or destroy them but she told them that neither would happen until she had her revenge. She fought Tiger Claw but he managed to trap her and prepare to use the blades to kill her but the turtles freed her and helped her fight Tiger Claw, during the fight both the blades were frozen by Tiger Claws ice gun, which made them brittle enough to be broken, thereby lifting the curse on Casey and Alopex managed to defeat Tiger Claw.