The fight against King Arthur at Misty Lake is the first time Sonic faces the fallen monarch in Sonic and the Black Knight. Having pursued Merlina the Wizard since the game's opening cutscene, King Arthur finally catches up with the errant royal sorceress beside the sunken palaces of Misty Lake. However, the King didn't reckon for her new protector, Sonic the Hedgehog; nor his freshly-retrieved weapon, Caliburn, the sacred sword.
This fight takes the form of a running battle, as the black knight rides his horse away from Sonic, periodically conjuring up Knights of the Underworld to impede the hero's pursuit. The king will stop three times for set-piece sword battles; these take the form of Quick-Time Events where the player must swing the Wiimote to counter Arthur's sword-slashes. Be careful on the final slash after the grindrail segment; the knight delays his strike to trick you into parrying poorly.
Although the king is defeated in combat here, the Scabbard of Excalibur renders him immune to actual harm. Arthur withdraws, mocking Sonic as "A fool of a knight, not even worth slaying." Merlina and Caliburn conclude that Sonic must consult with Nimue in order to learn how to defeat the king; but first he must take Caliburn to Camelot Castle, in order to repair the sword's dulled blade.