a sense of history
Many years ago, the power of Chaos threatened the most advanced civilization this world had yet seen. The Island of their residence was held suspended in the sky, held by Chaos. But the Island had not always been this way. Once it had been earthbound, in the place of its creation. But civilization had made great leaps and bounds; when a meteorite threatened to destroy the Island and all its people, drastic measures would be taken. The emeralds containing the power of Chaos were mined, and these emeralds, with their infinite power, were used to lift the Island, to unchain its anchor, to break free of the laws of physics and create a Floating Island, that the meteorite might strike the ocean and spare the people of the Island. The plan worked. But many years passed, and there were many who wished the Island to be again returned to the sea. When two bold scientists, brothers Edmund and Dimitri, proposed siphoning the power of the emeralds, draining them gradually, and thus slowly returning the Island to the waters below, this proposal was struck down. Edmund accepted the magistrate's decision, but Dimitri refused, taking it upon himself to complete the task he and his brother had worked so hard to create.
But the power of Chaos could not be fathomed. The siphon absorbed the emerald's power too quickly, and destructed. In the moments that followed, Dimitri himself, not the destructed siphon, absorbed the power of the emeralds. Only one of the emeralds remained. Mad with power, Dimitri sought to exact his revenge on the council that denied his proposal, on the society that had not appreciated his genius. He erected a behemothic tower to stand a sign of his infinite power, the power of Chaos with which he had been bestowed. But his tower, unable to withstand his unfathomable power, crumbled. Dimitri was buried beneath it.
The civilization decided that it was their incredible technology that had caused this disaster. Vowing not to let their technology become their bane, they buried many relics of their advanced technology and sealed them away in the Grand Conservatory. Edmund, brother of Dimitri, was appointed the first Guardian of the last remaining Chaos emerald; his duty was to protect the emerald, to prevent another disaster from arising out of its power, and to protect the people of the Floating Island.
Many generations passed. Edmund passed down the role of Guardian to his eldest son, and with each new generation the title of Guardian was passed down.
In time, the civilization inexplicably vanished. The presiding Guardian, the one they called Knuckles, had grown up in the great City, but when his father walked into the wall of flames and disappeared, Knuckles was forced to accept guardianship, perhaps too soon. But the City was gone, and the Guardian didn't understand. He turned to ask his father, who surely knew, but his father was not there. He could not remember when he had last seen the City and his fellow people. All he knew is that it had once been there and that it was not there now. He found a few friends, but there were few left on the Island. He felt empty, but knew that he was the Guardian and that the Chaos emerald which held the Island afloat was his responsibility; his duty was to guard it.
He had failed his duty.
The Floating Island had fallen into the sea and he had failed his duty. The location of the Chaos emerald was unknown; it had been lost in an Entropic struggle between the rebel hero Sonic and the dictator of Mobius, Doctor Robotnik, who had seized the throne, betraying the King whom he had served in the Great War. Robotnik had erected a tower that, with the power of Chaos, could eventually destroy the world, and certainly subordinate any rebellions against his empire, effectively winning him complete hegemony. But in an unforeseen turn of events, he had left his satellite open, and his own satellite was turned against him. The tower was a dead, broken shell. But it still held the emerald. Robotnik beat the crippled Sonic to the top of the tower, and in the ensuing struggle, Robotnik's hovercraft was marred by rubble, and the emerald was knocked into the malfunctioning hovercraft, which took off of its own accord. The hovercraft took an erratic and unpredictable flight pattern, and had still not been found by either Robotnik, or the Guardian Knuckles, who had taken up the search. Driven by forces he cannot fathom, Knuckles seeks the emerald to restore it to its rightful place and fulfill his duty. But the power of Chaos is sought by evil as well.