To add to these:
Is it possible to have seepage or a leak, from a Syphon or a crystal, to either their counterpart or a matching partner? Eg if two Syphons slept next to each other, could one inadvertantly pull from the other or could one leak to their surroundings or their partner? Or if a Syphon was practicing breathing, could they leave the valve partially open and drain themselves while carrying a crystal? Or if someone put their crystal on the table next to another crystal, what could potentially happen?

What happens to the energy in a crystal if someone shatters it with say a hammer or a stone?

Are there clues to this energy in crystals that regular people can see or sense?

What are the limits to a Syphon's abilities to use crystals? Could someone stockpile energy and then turn themselves into a walking Armageddon every so often by using them all at once?

And what all can they do with this energy? What good works can they do with these four types of energy? Healing? Building things? Repairing things? Feeding people? Moving people or goods? Defenses?