King Bull Sparra was the Sparra king who inherited the Sword of Martin from the King Bloodfeather. He was clever but insane at the same time. King Bull was the brother of Dunwing and uncle of Warbeak.
While hunting for worms in Mossflower Woods with his brother-in-law- Dunwing's husband- Greytail, he was attacked by Asmodeus Poisonteeth and dropped the sword. Asmodeus then took possession of the sword, to which King Bull Sparra ordered Greytail to retrieve the sword for his king. Greytail made an attempt to get the sword from Asmodeus but was bitten by the adder. He miraculously, did not die instantly, and pon returning to the Sparra court, Greytail told Dunwing what really happened while King Bull Sparra told everyone else that Greytail's injuries were due to a starling fight and pretended that he still had the sword. Greytail died of his wounds shortly after.
King Bull Sparra captured Matthias when he climbed up to the Sparra court. Due to the pleas of his sister, he spared Matthias, but kept him as a slave for her. He had a special fondness for candied chestnuts, of which he demanded Matthias repeatedly. King Bull noticed that Matthias's belt was of the same leather as his scabbard and took it from him. On the day that Matthias escaped the loft, King Bull was led to believe that Asmodeus was spotted in Mossflower dying with the Sword due to a rumor started by Dunwing. After hiding the scabbard and belt in the back of an old armchair, King Bull led a party of warriors to find the snake. Finding nothing, he flew back to Redwall Abbey. He saw Matthias on the roof waving the scabbard and belt for Jess Squirrel to see. King Bull attacked Matthias immediately and dug his claws into the belt but was knocked senseless by the mouse's scabbard. He fell off the roof and dragged Matthias down with him.
His body was found later along with the injured Matthias in the Abbey pond.