The Black Knight or King Arthur is a fictional character in the Sonic the Hedgehog series, first appearing in Sonic and the Black Knight. He was first believed to be the main antagonist of the game, but that role was given to Merlina upon his defeat. He is voiced by Gavin Hammon in the English version.
One day, King Arthur became corrupt when an unknown evil came from his scabbard and tainted him, becoming the Black Knight. He has strong relations with the Knights of the Round Table, as they still serve him despite his change. His powers include using his blade, Deathcalibur, to summon Underworld minions to do his bidding and firing magical bolts on top of his impressive sword skills. His scabbard grants him immortality, making him impossible to defeat without obtain the three blades held by the Knights of the Round Table.
Sonic faces the Black Knight twice during the game. The first time is shortly after obtaining Caliburnd, but lacking both the swords and the skill, he is unable to defeat him and the Black Knight leaves after deeming Sonic not worth his time. The second time is a more heated duel at Castle Avalon where Sonic is able to use the Knight's swords to nullify the scabbard's power and defeat him.
After being bested by Sonic, the Black Knight fades away, leaving nothing but his scabbard. When Sonic brings the scabbard to Merlina, she reveals that King Arthur was never there and it was merely part of her plan to acquire it for her own ends.
Despite the fact that he is also first seen as King Arthur by everyone's eyes, Sonic's blade Caliburn reveals that since he is a legendary sacred sword, his duty is to decide who is fit for the crown. So that would technically mean that Sonic was the REAL King Arthur the entire time.
His theme song is [[Fight the Knight, a song by Crush 40 for the two boss fights Sonic has with him.
- An early rumor stated that King Arthur might look like Dr. Eggman, possibly brought about due to Eggman taking the role of King Shahryār in the previous Sonic and the Secret Rings.
- The evil power that had corrupted King Arthur might also have been the cause of the genie of Aladdin, Erazor Djinn, to turn evil and attempt to destroy the Arabian Nights world.
- The Black Knight and Erazor Djinn both have attributes of their personality that are quite similar. Both were characters from another story turned evil, they are power craving brutes with incredible power and they each have to deal with Sonic and his female partner (Shahra for Erazor Djinn and Merlina for the Black Knight).
- His sword Excalibur, changed and is now called Deathcalibur. It was restored near the end of the story.
- It's wondered what happened to the world after the Black Knight was defeated. If he was really meant to be King Arthur, and yet Caliburn reveals that at the end that he decides who is worthy of the crown which points out that Sonic was really King Arthur, it is wondered who is ruling the land with Sonic's return home and the Black Knight slain.
- The Black Knight shares many similarities to Nightmare, a character from the SoulCalibur series of games.
- 1.) They both have a dark knight sort of theme.
- 2.) They both have Zweihänder type weapons.
- 3.) They both oppose the "Calibur" type of weapons(Sonic's Caliburn, and Siegfried's Soul Calibur).
- 4.) They both use dark polar opposites of their rival swords (Black Knight-Deathcalibur, Nightmare-Soul Edge).