In ancient times, Solego, (the eponymous and immortal Chaos God) destroys everyone who opposes his iron-fisted rule — until a young wizard named D'Shane manages to split Solego in two by imprisoning the sorcerer's immortal mind in a crystal cage and his mystical powers in its gold setting. To ensure Solego's eternal imprisonment, D'Shane keeps the halves separated by mounting them onto a giant jade block.
Many centuries later, archaeologist and professor Simon Potsherd removes the two artifacts from the jade block and fixes a chain to the crystal for handling. He arranges to have both artifacts transported to Cape Suzette, but during a battle with the Air Pirates, the gold setting ends up lost in the ocean. An ordeal at Higher For Hire arises when Solegos spirit possesses Rebecca Cunningham through the crystal. After a minor tussle, Rebecca is freed, and Baloo and Kit drop the crystal deep into the ocean.
Fifty years later, a lucky fisherman finds the crystal and brings it to the museum where the gold setting now resides (as it turns out, Scrooge McDuck donated it after he found it during a diving expedition). Fat Cat and his cronies sneak into the museum later that evening to steal the crystal, and though they foil his plans, the Rescue Rangers have a brush with Solego, who nearly manages to escape his 'prison' by possessing Dale and Fat Cat. A well-timed electric shock to Fat Cat keeps Solego's two halves apart, and the Rescue Rangers have a pair of crows carry the crystal and the gold setting in different directions to keep them separated.
The crow carrying the crystal grows tired during his flight and accidentally drops it into a car with a computerized brain — which, as fate would have it, ends up delivered to Pete in Spoonerville. When Goofy gets a look at the car, he begins to think something has haunted it; Later that night, Solego uses the car to learn from a TV report that the gold setting has ended up back in Scrooge's possession (it now sits in the Money Bin) after it ended up in a pawn shop. Goofy sees the car hack into his television set and freaks out, and he and Pete try (to no avail) to get Solego out of the car. Solego entraps Goofy and Pete inside the car's interior, then forces the latter to turn the engine on so he can get to Duckburg. The car ends up going over a cliff, though not before Goofy and Pete escape through the windows.
Solego uses the wrecked car's still-working phone to hire Spoonerville's tow service, which tows the car to Duckburg and writes off the bill to Scrooge McDuck. The next morning, Fenton Crackshell takes a look at the car (which Scrooge insists he knows nothing about) and finds the crystal inside. Under Solego's spell, Fenton summons the Gizmoduck armor, which Solego quickly kicks Fenton out of. Solego then uses the Gizmosuit to break into the Money Bin, but discovers that Scrooge sent the gold setting to St. Canard for cleaning. After Solego leaves the Money Bin, Scrooge, Fenton, and the nephew trio meet with Professor Potsherd's son, Bisk, who reveals the backstory of the Chaos God and D'Shane. Once they have all the information on Solego, Scrooge sends Fenton to St. Canard, then calls up S.H.U.S.H. Headquarters to get in touch with the only person in St. Canard who can help now: Darkwing Duck.
Over in St. Canard, J. Gander Hooter briefs Darkwing and Launchpad on their mission. However, the duo (and Fenton) arrive too late to stop Solego from finding the setting, and when Solego finally brings the crystal and the setting together, he assumes his original form and wreaks havoc across St. Canard. During his fight with Darkwing and his compatriots, the Chaos God disintegrates Fenton's Gizmosuit and turns Launchpad into chopped liver (literally), which leaves Darkwing to stand alone against an immortal sorcerer. After a brief cat-and-mouse battle between the two, Darkwing accidentally defeats Solego by reflecting his own powers back upon him, trapping him back in the crystal exactly like D'Shane did centuries earlier.
After a denouement at S.H.U.S.H. headquarters with Bisk Potsherd, the medallion segments are once again embedded in the jade block, sealed away, and buried deep beneath Scrooge's Money Bin, to hopefully be forgotten again.