[Staircase]

You have to let a skeleton cast any spell on you while standing on one. Do that for all four squares.

And i totaly agree with darkshadow's post (Im just to lazy to quote it atm =p) Im on year 16 and still training so i can beat the final bosses. There difficult in 1p -.-. Of course i cant judge the multiplayer because ive never used it (only have 1 gba), but i imagine it would be fun.