I didn’t get to the back-story yet, but here is the character file.
Fantasy Grounds File: Level 3 “Human” Eldritch Knight.
The Cursed Blade is truly the sword, not the human body. But no one knows this. As a magic sword his role was more protector than slayer, so he has animated the knight’s body as a tank-style fighter, with heavy armor and a shield. As a result he is extremely difficult to destroy.
However, he can make himself burst into flame at will (cantrip green-flame blade), and project flame as a weapon (Fire bolt & Burning hands). He is self- repairing and can extend that to other items (cantrip mending).