Student Belt Recipe = Almost infinite Crystals

[Zechnophobe]

There may be others that do this, but the Student Belt Recipe works.

It costs 4 Crystals, 4k gold, and 40 mana to make the student belt.

With Artifactor, you can destroy the student belt and receive 5 crystals. This means:

4k Gold + 40 Mana = 1 Crystal.

Worse yet, but at least in KBAP, the student belt worked if it is in your inventory OR equipped to your character. I'll have to test this, but that may mean you can make a large number of these, and get runes after pretty much every fight!