King Arthur's Soul Surge is King Arthur's Soul Surge technique in Sonic and the Black Knight. When using this technique, King Arthur creates a circle of electricity from his sword, Deathcalibur. This move can, however, only be used in multiplayer mode as it is the only time where King Arthur is playable.
When Arthur is performing his Soul Surge, he raises his sword, Deathcalibur, as high as he can into the air. He then releases several purple lightning bolts from the tip of Deathcalibur, down to the ground, that encompass the entire battlefield. The lightning bolts then starts rotating around Arthur, while being continuously generated for a short time from Deathcalibur, forming a dome around Arthur.
In order to perform Arthur's Soul Surge, Arthur's Soul Gauge must contain some energy. To activate this Soul Surge in gameplay, the player must press , and to attack with it, the player then has to swing the Wii Remote. To cancel the move while being used, the player must press again. Using this Soul Surge deceases the energy in the Soul Gauge, and if it runs out of energy, the move will end. This technique lasts for about three seconds. Any lesser enemies that come into contact with the dome generated by Arthur's Soul Surge are either instantly destroyed or receive massive damage. If other players' characters get hit by this dome, however, they take damage and will continue to take damage for as long as they remain inside the the dome while it is active. However, by continuing to guard, a player can counter the continuous damage. Also this move can only be performed while the Arthur is standing on the ground.
- King Arthur's Soul Surge was also used against Sonic during their second battle in Faraway Avalon. During the battle, King Arthur will shout "Roar! Deathcalibur!" and will raise his sword and send out one or multiple purple lightning bolts behind him in an attempt to hit Sonic. It can easily be evaded by performing the homing attack along the far right or left sides of the area.