Blades of Vengeance

In the first level, play through the first part of the level all the way until you get to the door that takes you to a new part of the level. This is the door near the button on the ground that pops out a treasure chest behind you. Use your jump attack to jump onto an invisible platform just over the left part of the top of the door. It's fairly difficult to reach, unless you are the girl, but you can reach it with any character. Once you're up there, jump up and to the far right, there's another invisible platform against the wall. Once you're against the wall, just keep jumping up until you get to the secret door!

Inside the door there are several chests with gold and silver and all kinds of potions, several power stars, and 7 more doors. The doors will take you to the different levels of the game. The first door takes you to level 2, the second to level 3, etc...