Exchanging crystals with runes
 

Hi, I want to make exchanging magic crystals with runes (all kinds) an option in the shop in front of the dwarf capital. I guess this should be scripted in one of the .lua files but can't find it. Does anyone know how to do this? Many thanks in advance.
Edit: the ratio may be set as 20 crystals -> 1 rune & 1 rune -> 5 crystals so as to make alchemy worth taking but not overpowered.

Seems like this would be unbalanced in favor of the warrior who is swimming in extra crystals compared to the mage.

then make the ratio for warrior/paladin/mage different, such as warrior 40:1, paladin 30:1 & mage 20:1. first thing I want to know is how to do it :D