Do nothing. ATA gives them out every event, and each tier(or every 2) of legends usually gives an xtal
These are the ways to obtain Health Crystals: - From legends. - Sometimes when you log in. - From quests, although it's a really low drop rate. - Purchase them through the Oracle. Next time, please use Dillybar's Questions thread for questions like this. I'll be locking the thread as the question has been answered!