There’s this old movie from my childhood that I’ve never been able to find. I don’t exactly remember the plot but I do remember this old man had this magical sword that was chained to its sheath. It had an actual chain that couldn't be unlocked. Only the right person at the right time could unsheathe it. The old man gave it to this man who was “the one.” When he was attacked he was able to unsheathe the sword and it would transform him into this hairy beast like man who was unstoppable. I remember the guy having a family that was with him. Any thoughts?