You simply put a crystal into a bag - and if you find one with a larger value - you exchange by drag&drop. You can't combine - let's say - 2 small air crystals into one medium sized one.
I took the smaller one out into my inventory (via drag) and put in a larger one - or depending on my enemies, put in a different crystal.
No skill required.
Kiya
And welcome to the forum, Warpig <img src="/ubbthreads/images/graemlins/wave.gif" alt="" />
