In the magic-rich environment of the Earth in my novel, I tried to make the different schools of miracle-making logical and believable (at least, to a point!).
There are the Ether-manipulators, both male and female, who are generally benign and performing their feats by drawing the Power from the Cosmos itself.
There are of the priests of the various gods, whose ethics depend on their masters'. Their miracles are dependent the Power available from their deity...in other words, the more powerful the god, the greater the miracles.
Then you come to the necromancers, who are always evil, who are skilled by much study and by making offerings to the Nether Beings of the Abyss, powerful creatures who, fortunately, seldom disturb the world of man. The necromancers have in many ways the most powerful spells but their school of thought is also the most dangerous to the practitioner.
If you've read this, thanks a lot! Now you get back to whatever you were doing.