You're Prince Lightstar, with the quest to conquer and slay Baron Dark, who holds the half of a mighty crystal called the Lightstar Crystal. With that crystal he can change anyone with an evil heart into his skeleton slave.
The game is a 2D sidescrolling platform game with 3D pre-rendered graphics, with about 100 types of enemies for you to slay with the weapons you possess. You need to complete 21 levels filled with demonic evil creatures before you can fight the Baron Dark himself, with 3D rendered cutscenes inbetween some levels.
Based on a short-lived toyline/animated series franchise (a la Transformers or G.I. Joe) of the same name. Don't worry if you've never heard about them, save for the moderately cool skeleton toys, you didn't miss anything.