Board Thread:Game Discussions/@comment-25178219-20141229104705/@comment-25732250-20141229165656

Correct, the Drop rate for the Crystals is probably 50% lower than the other tiers and it gets better when you reach the Kingdom of Darkness, the rate in this stage is so low that I get a piece out of 6 runs.

So be patient and plan your attacks to get the most out of every Stamina bar.

Good luck.