Astrium is an exotic element formed from remnants of the Empyreal known as Omega. It's a by-product of iriil decay. Over the millennia, it has coalesced upon the various gravitational bodies across the Starmourn Sector. It is highly sought after, and many races have set up mining and refining operations to acquire its power, mainly as an energy source.
It has three main forms: Low density, destabilized Astrium, the "natural" and inert form which is mined. High density, destabilized Astrium, an extermely volatile form produced by proton bombardment and often used for explosive devices. And high density, stabilized Astrium which is used as the energy source for quantum power cells.