So, I've played this game for a few days now and was having a blast so far. Really great and unique gameplay!

But now I'm at level 16 and can't find the spell in this world. It's the level where you start in a small quadrat of unpassable walls with mirrors in it. On the map are three 'X' showing.
When I fly through the mirrors I get outside and can finally build up my castle. I won the mission and destroyed the red mage. I also investigated the whole map, especially the statues and stone formations, that gave spells earlier or made them appear somewhere else on the map. No luck this time... They seem to trigger nothing. The statues stand in a cirle and are surrounded by mirrors. When I fly through any of these mirrors I get teleported in the circle of statues, nothing else happens.

Any hints at how to find the spell?
And I know this has been asked before, but is there really no guide to be found anywhere? I want to find all the spells at least, but this seems to be very hard without a guide, when the problems start at level 16 out of 50.