From Sonic Retro
Faraway Avalon is the seventh stage in Sonic and the Black Knight for the Nintendo Wii. Built on an island in the Grand Kingdom's southern sea, it is King Arthur's vast castle complex; a fairytale fortress of alabaster stone and ivy-covered walls. The castle features a concourse of apparently infinite length, and it is here that Sonic fights his last battle against the Black Knight.
After defeating Sir Percival in Molten Mine and expropriating her Sacred Sword, Sonic now has the full set: Lancelot's Arondight, Gawain's Galatine, Percival's Laevatein, and the hedgehog's own Caliburn. According to Nimue, these swords taken together have the power to dispel the immortality bestowed upon King Arthur by the Scabbard of Excalibur.
Arriving upon the King's fortress-isle at sunset, Sonic is met immediately by the Black Knight himself, who concedes that "It seems your impersonation of a knight has improved... somewhat." This boss fight is considerably more difficult than the first confrontation in Misty Lake, but in the end Sonic triumphs, and cuts down the King after thwarting the Scabbard's power with the Sacred Swords.
What would apparently be the end of the game, however, proves only to be the end of the first arc. It is with no small amount of surprise that Sonic watches the King dissolve into black mist, just like the standard Knights of the Underworld. Picking up Excalibur's Scabbard, the hedgehog races back to see Merlina in Camelot Castle to get to the bottom of this mystery...
For a long time, the boss fight is the only mission available in Faraway Avalon, but others do slowly become available:
Items which can be acquired in the Faraway Avalon missions include: