The Kingdom Stone is the crystalline concentration of the energy supplies of the starship that brought the ancient dragons to Avalice. It's used by the avalicians to power their technology. According to the Royal Magister, the three kingdoms have depended on it for centuries.Before its destruction, the stone resembled a sparkling crystal orb. It had the colors of opal (purple) and sapphire (light blue). After its destruction, it becomes a crystalline vortex of the same colors and has most likely become the planetary ring of Avalice.
By the time Lord Brevon and his army crashlanded on Avalice, the Kingdom Stone's power was fading, unable to keep up with the energy demands. Prompting to a seeming energy crisis, Mayor Zao hires Spade to help his Soldiers to steal it from the ancient temple in order to not only preserve his city's power, but also to increase his chances for a re-election. Around that time, Brevon murders the king of Shuigang and brainwashed his son, the at this point only prince, Dail, to steal the stone to recharge his Dreadnought so he could continue his galactic conquest, leaving the three kingdoms on the approach of civil war.
After Lilac manages to convince the armies of Shang Tu and Shang Mu to unite against Brevon with the Holodragon, a large assault on the Dreadnought's refueling station takes place, but not before the warship makes liftoff with only Lilac, Carol, Milla, and Torque getting onboard. When Lilac and Carol almost succeed in disconnecting the stone from the ship's mainframe, Brevon forces them to stop their attempt when he captures Milla and turns her into a mutant. Milla is defeated and falls into a death-like coma, which enrages Lilac and Carol, who break through the last of Brevon's defenses and make their way to the power core of the Dreadnought, where they confront and defeat Brevon. After the batle, the Dreadnought explodes, taking the stone with it. When all hope was lost, it reincarnated as a crystalline vortex that hovers over the planet, with the Magister stating in the epilogue that a new opportunity has befallen Avalice.