Where can i find dark crystals?

[Human Devil]

I need to get a Dark Crystal so i can get a Orichalcum+. But what enemies drop it?

[Tavrobel]

Dark Crystals are dropped by Air Pirates, in Port Royal, when at level 20, and at Land of Dragons when it becomes LoD battle level 35, 8% drop rate.

Orichalcum+ is given at certain events throughout the game. Drop rate of 100%, of course. Since there are only seven, the drop rate otherwise is the measly rate of 0.0%.

Seal Atlantica, Seal 100 Acre Wood
Finish the Goddess of Fate Cup
Obtain at least one of all Synthesis materials
Brink of Despair (WtNW)
Central Computer Mesa (before CPU)
Sunset Terrace