Fal Divi

The arcane spell Fal Divi is one of the perhaps most powerful spells ever created by the Cult of Runes.

The mages did discover that the strict division into arcane and divine magic was to their disadvantage, closing the door to many useful spells. Thus the creation of this spell. Casting this spell allows the mage to actually cast a divine spell of chosing. Needless to say that this is a tremendous power, especially since even the more advanced divine spells still have the mana cost of Fal Divi.

Its power is also shown in the fact that the Cult of Truth doesn't have such a spell for arcane magic.