SpoilerShow
You need to use the 9 plates to cast the spell shown, there are 3 spells
1. Fireball
[][]X
[][]X Door
[]X X
2. Ice shards
X[][]
X[][] Door
X[][]
3. Lightning bolt
[]X[]
[]X X Door
[][]X
1. Fireball
[][]X
[][]X Door
[]X X
2. Ice shards
X[][]
X[][] Door
X[][]
3. Lightning bolt
[]X[]
[]X X Door
[][]X