This is driving me nuts.
I have tried with the following boosts:
Hero Potion - gives boosts to MHP, ATK, DEF, AGI
Fortune Potion - gives boost to LUK
Brain Potion - gives boost to MMP
That only leaves MAT or MDF boosts - but I had to use the Cosmic Potion in order to get 4 MDF boosts for the Crystal God.
Any suggestions?
Anyone actually managed to do this?