High. The White Knight is a physical name that augments the user's physical abilities, providing enhanced durability as well as speed. Hanno was able to compete with the the current Black Knight, a member of the Calamities, so it can be assumed that the Name is extremely powerful.
The White Knight's role is to stand for Justice. He is unable to commit any acts of evil, or to perceive any act he does as unjust lest he be judged by the same power that was bestowed upon him.
The lives of most White Knights have centered on fighting Villains, although there has been a tendency among those born to Callow to instead specialize in fighting beasts and monsters, leaving the traditional rivalry with the Praesi Black Knights to the Shining Princes or Princesses.
The White Knight, like many other heroes, mainly relies on inspiring others to his cause. He can cause regular soldiers to fight with the ferocity of ten men. He is also dangerous on his own, employing light that burns whatever it touches.