Quote from Dragon_Heir >>

Both phlogiston and crystal spheres where ideas from alchemy. The element of fire was phlogiston, which would be better connected to fire elementals, perhaps a space fire elemental variant. Meanwhile, crystal spheres were the explanation for planet orbits, before Newton realized it was gravity. 

 I was aware that phlogiston was an old alchemical theory, but not about crystal spheres. I absolutely love the idea of old, outdated pseudoscientific theories being expanded on and implemented into a fantasy setting.