Yeah, that room with all the characters is the door to the last boss, you have to beat all those people to open it up.
Make your way through, opening every single door, going to every single room, fighting every single clone, until you beat them all.
The purpley crystals represent warp / save points, the yellow crystals represent save points. And, obviously, restock / health points.
The Maze takes like an hour or two to beat...