Righteous Magic enhances the priest's physical powers.
The game engine applies max damage to this by setting the caster's DAMAGELUCK modifier (which accounts for the seemingly random variation in damage that a character can do from one hit to the next) to its maximum value, 20, for the spell's duration. This is effectively a longer duration version of Offensive Spin or Kai with a required cast time.
In-game description Edit
|“|| Righteous Magic|
This is a powerful combat spell that enhances the priest's physical prowess, transforming him into a juggernaut of destruction. The effect adds 1 temporary Hit Point per level of the caster, adds 1 point of Strength every 3 levels of the caster (to a maximum of 25), and causes every successful hit to inflict maximum damage. The effects last for the duration of the spell or until dispelled.