The Black Knight (黒騎士 Kurokishi) is a large centaur mamodo who is one of the Mamodo World's strongest warriors and a guardian of the Mamodo World who fights for justice. His owl companion Fukurou [フク口ウ, which literally translates to "Owl" (梟)] scouts for criminal activities and mostly talks in Black Knight's stead.
Fukurou proclaims that the Black Knight is Demon World's strongest warrior. However, the Black Knight has a major weakness: Whenever he dashes forward, he is unable to turn his body until he makes a complete halt and he usually doesn't stop moving unless if he is stopped by a wall or a cliff.
The Black Knight has a white spellbook, protected in his mansion. His White Spellbook has the power of "supression," negating and absorbing enemy spells and to be able to use the enemy's stolen spells with their spellbooks ultimately turning colorless after losing all of their spells. However, in the current Battle to Determine King of the Mamodo World in the first movie, a mamodo teenager named Wiseman stole the white spellbook and snuck into the Human World when he traded places with Zatch Bell.
With the White Spellbook stolen and with Zatch and Kiyo appearing in Mamodo World and when Fukurou found them, the Black Knight suspected Zatch and Kiyo that they stole the spellbook, locking them up in an impenetrable metal green cage conjured by the Black Knight's spiral lance. When Zatch argues with the Black Knight and when he was going to relatiate for Zatch's rudeness, the Black Knight spared their lives due to starvation.
Later, after Zatch and Kiyo were freed from the Black Knight's cage spell by the school headmaster, Black Knight and Fukurou learned the truth and brought Zatch and Kiyo back to the tree where they first entered the Mamodo World from Human World. The Black Knight would be powerless without his White Spellbook if he were to go into the Human World (due to spells being restricted to spellbooks in the Human World) so he and Fukurou put their fates on Zatch and Kiyo to defeat Wiseman.
Description: The Black Knight throws his lance at the ground near the enemy, summoning snakes that form into a large, impenetrable metal cage to trap his foes, usually criminals or suspects. The cage cannot be destroyed and the only known users who can dispel the cage into snakes are the Black Knight and the School Headmaster. The Black Knight can cast this spell without providing a spell incantation.