Trivia: Star Christopher Lambert has very poor eyesight, and as a result, he accidentally injured both himself and co-star Michael Ironside during the filming of an action set-piece.
Trivia: The producers didn't want to make a sequel to the original, but were pressed to do so by foreign investors due to the original being a hot-seller on VHS. During production, filming became a nightmare, as the script was constantly being re-written to contrive different ways to continue the story, and the film went over budget, causing the insurance companies involved to take over production and further "mess with" the storyline and effects to get it done quickly and cheaply. Director Russell Mulcahy was so ashamed of the finished film, he walked out of the premier before the end of the first act, and co-stars Christopher Lambert, Sean Connery and Michael Ironside have all admitted that the film was absolutely terrible. Lambert only finished filming because he was contractually obligated to the sequel, whereas Connery only made the film due to his friendship with Lambert and the steep paycheck he received, which he wanted to donate to charities he supported.
Trivia: This film's plot (ret-conning in an extra-terrestrial origin for the immortals) was so notoriously hated among fans of the original film, it was completely disregarded in subsequent sequels, and an alternate cut of this film (removing all alien references) was later released to appease fans.
Answer: Killing another immortal grants you their life energy. The energy returned his youth and powers.
lionhead