- "Do you know what that really is?"
"Yeah. About sixty million credits worth of refined coaxium."
"No. It's the blood that brings life to something new."
- ―Enfys Nest and Han Solo
Coaxium in its raw, unrefined state was a very volatile and highly explosive substance and had to be refined in order for it to be stable enough to be stored at room temperature. Unrefined coaxium, once mined, would gradually begin to destabilize and turn red in color before exploding violently if not stored properly in a temperature controlled environment. One such coaxium refinery existed on the desert planet of Savareen.
The hyperdrive reaction chamber of a starship was coated in coaxium, which, when energized, allowed the ship to travel through hyperspace. Coaxium, when used as a fuel, was so potent at energy generation that just a small amount of it was sufficient to power an entire fleet of ships. This made it extremely valuable and it was therefore highly sought after by many. The Galactic Empire transported large shipments of coaxium under high-security measurements, with the intent of gaining complete control over the production of the substance.
By the age of the Galactic Empire, coaxium was a highly valuable substance sought after by the Empire as well as various criminal organizations; the White Worms, the Pyke Syndicate, and the Crimson Dawn among them.
Thirteen years prior to the Battle of Yavin, a young Han acquired a small amount of coaxium, and he and his childhood friend Qi'ra attempted to use it to barter their way off of Corellia. He partially failed, only managing to secure his own escape, while Qi'ra was detained at the spaceport.
Three years later, Solo became embroiled in a plot to steal a shipment of the precious fuel from a 20-T Railcrawler conveyex transport on Vandor for Dryden Vos and Crimson Dawn. Due to the interference of Enfys Nest and her Cloud-Riders, Solo chose to release the tethers holding the coaxium rather than follow Tobias Beckett's orders to fly straight towards a mountainside. The Cloud-Riders' swoops were unable to hold up the heavy container on their own and were forced to drop it, causing a massive explosion that collapsed the mountainside.
Finally, Solo, together with Qi'ra, Lando Calrissian, the Wookiee Chewbacca, and L3-37 made the Kessel Run to obtain unrefined coaxium from the Pykes and bring it back to Vos in repayment for their past failures. This time, Solo succeeded, bringing the shipment to Savareen to be refined. He and his associates were soon confronted by the Cloud-Riders, who revealed Crimson Dawn's intention to use the coaxium to spread death across the galaxy.
Deciding to doublecross Crimson Dawn, Solo fed false information to Beckett, knowing he would sell him out to Vos, that he would be bringing two crates full of counterfeit coaxium, when in fact he was bringing the real shipment. Both Beckett and Vos were fooled by his ruse as the Crimson Dawn enforcers attempted to ambush the Cloud-Riders only to be fooled by decoys and empty crates before they were dispatched. Beckett soon took Chewbacca hostage and held him at blasterpoint to carry the coaxium off Vos's yacht, but Solo soon caught up to him and killed Beckett. Afterwards, he gave the coaxium to the Cloud-Riders to fund their growing rebellion. After declining Enfys's offer for Solo to join them, she provided him a single vial of coaxium, which he used in a sabacc game against Calrissian in which he won ownership of the Millennium Falcon.
Sometime after the Battle of Yavin, the MC80 Star Cruiser Aurora Flare was carrying a large amount of coaxium from the Redhurne system. Upon hearing the news of king Lee-Char's murder, the Aurora Flare crashed into an Imperial-class Star Destroyer, creating an opening for many other Mon Calamari cruisers to flee to the rebel-controlled Mako-Ta Space Docks.