In Celestite north of Victala City you will enter the "Lookout of Dreams" where you will find a crystal statue with a Munna in it. In Pokemon Celestite the crystal is large and cool while in Pokemon Nightmare it is small and found in a different area.
Theoretically there are dream crystals in every region though they may also be weathered down and possibly hidden from sight.
If you have a fangame or game re-make and want to use this then please read this journal first and ask my permission: [link]
Only for use by :
Pokemon Celestite by (me) Pokemon Chrome Crimson by Pokemon Forever Lost by Pokemon Bithynia by Pokemon Sky by Pokemon Frost Flame by Pokemon Aura Guardians by
Well Because the map is an ice map (the one you commented about the crystal actually) and there are supposed to be other light blue ice crystals around the map. Unless if that's a problem. Then I'll find another