Cathan was a member of the original Horadrim.
A devout priest and fierce warrior, he took part in the battle to bind Mephisto. Common soldiers were hard pressed to combat the Lord of Hatred's tides of undead, but Cathan found that by invoking the powers of the High Heavens and infusing them with the essence of fire, a bolt of great speed and intensity could be created and used by those otherwise untrained in magic. Thus was the origins of the Holy Bolt spell.
Cathan is referenced in flavor lore of the Holy Bolt spell.