"Blastia are devices composed of two parts: a body and a core. The body is responsible for controlling the magic that is generated by the core."

[Yeah, she's definitely reciting that from somewhere.]

The cores are like gemstones made of condensed aer. And aer is like... magic energy, but it's also a substance the planet needs to sustain life. Blastia can be used to power machines, and when worn on the body, allow humans to use magic.