One of the points that is made through the series though is that pretty much all the magic in the world comes from the Gods and that casting magical spells is basically accomplished by praying to them. The only exceptions being Klael, Bhelliom and, by extension, Sparhawk. Sephrenia makes some claims about the Delphae practicing witchcraft but it is never clear if that is just bigotry on her part or if that actually exists.
Near the end of the Tamuli, Zalasta shows up and tries to stop the wedding being held. He is clearly tossing around a fair amount of magical power even if Sparhawk has no problem blocking him. Where is he getting the power from though? All of the Gods he tried to work with are KIA by that point and I doubt any of the others would be inclined to help him given that it might put them in conflict with Sparhawk.