Quote Originally Posted by Slashley View Post
They're an extremely rare drop from 15AP I think, but relatively common from 25AP. Just keep at it.

Either way, you can convert 15 Holy Crystal of Light into one. That's quite expensive though, and chances are you'll find one or two before you get to 15.
At this rate, I'm probably going to have to exchange them... I grind the 25 AP quest very often