The Kingdom Stone is the crystalline concentration of the energy supply from the starship that brought the Ancient Dragons of the Before Time to Avalice. It's used by the Avalicians to power their technology. According to the Royal Magister, the Three Kingdoms of Avalice: Shang Tu, Shang Mu & Shuigang have all depended on the Kingdom Stone for centuries.
Before its destruction, the Kingdom 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 became the planetary ring that surrounds Avalice.
By the time Lord Brevon and his army crashlanded on Avalice, the strength of the Kingdom Stone's power was fading, unable to keep up with the growing energy demands. Desperate to avert an energy crisis in Shang Mu, Mayor Zao hires Spade to help his Soldiers 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 had invaded Shuigang, murdered the King and brainwashed his son Dail, the only Heir to the throne, to steal the Stone to recharge his Dreadnought so he could continue his galactic conquest, leaving the planet on the approach of civil war. However, Brevon's plan to turn the Three Kingdoms against each other backfires after Lilac manages to unite the armies of Shang Tu and Shang Mu with the aid of the Holodragon. Both armies then launched an assault on the Dreadnought's refueling station in the snowfields. But by the time they reach the Dreadnought, it makes liftoff with only Lilac, Carol, Milla & Torque managing to get onboard, where they come face-to-face with Lord Brevon and the full force of his Army.
After defeating an upgraded Syntax and a mutated Serpentine, Lilac and Carol make their way to the Dreadnought's power core. Just as they were about to reclaim the Kingdom Stone, Brevon stop their attempt by capturing Milla and turning her into a mutant, forcing her to attack her friends. Milla is defeated and falls into a death-like coma, enraging Lilac & 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 battle, the Dreadnought explodes, taking the Kingdom Stone with it. When all hope seemed lost, the Stone reincarnated itself as a crystalline vortex that hovers over the Avalice, spreading unlimited energy across the planet, marking a new beginning for the people of Avalice.
The new form of the Kingdom Stone may have improved life on Avalice for the past 2 years, but the destruction of it's physical form has resulted in the awakening of Merga, a bioengineered Water Dragon from Avalice's oldest and deadliest war. As a result of her ruthlessness and warmongering, she was sealed in a crystal prison locked by the Kingdom Stone's power and hidden deep in the ocean off the coast of Parusa. Now she has returned, seeking vengeance upon the Avalicians for sealing her away and sets out to "purify the world" by ressurecting the ancient superweapon, Bakunawa.