The sacred swords are objects that appear in Sonic and the Black Knight. They are four weapons use to protect the world of Camelot. They are used to dull Excalibur's scabbard's power during the battle with King Arthur, and to form a barrier around Castle Camelot with the barrier stones.
Sonic and the Black Knight
During the first part of the story mode, Sonic defeats each of the knights in turn and takes their swords. After the second battle against the King Arthur, Sonic uses the power of the swords to nullify King Arthur's immortality and finishes him. Later, the sacred swords (and Caliburn) are placed in shrines located in the four corners of Camelot to prevent the spread of Merlina's dark magic: unfortunately, the barrier is not strong enough. Finally, Sonic and Caliburn confront Merlina in the Dark Hollow, while the knights and Nimue look on through Nimue's pool. When all hope is lost, Sonic still refuses to give in. On Nimue's command, the knights throw the sacred swords into the pool. Caliburn merges with the other swords and transforms into the legendary Excalibur, with Sonic becoming Excalibur Sonic, before entering the final battle against the Dark Queen.
List of the sacred swords
Long-lost light of the sacred sword
The long-lost light of the sacred sword was used to aid Sonic when he fought The Dark Queen granting Caliburn the power to become his true blade, Excalibur. It also gave Sonic a golden armor which granted him powers such as flight, and increased power. The light was summoned when the knights offered their swords to Nimue's pool when it shone with the light.