Change your location. You can not get your crystal high enough at the Forest of Mirrors (which is up to level 5) or something.
As far as I know:
Forbidden Gateway = Up to level 8/9.
Lair of Antharas = Up to level 10.
Some L80+ Raid Boss / Zaken / Baium = Level 11 and 12 (don't know which ones exactly, use google
).
Antharas / Valakas = Level 13 (S Grade SA).
Forbidden Gateway is the perfect place to get your level 6 crystal. ;p
