On second thought, Jason Blood would make a much better guinea pig than John Constantine to see if its safe to Danner a magician or sorcerer.
Jason Blood had the demon Etrigan bound to him by Merlin, "cursing him with immortality". His immortality would compensate for any flaws or side effects with the empowerment process, which OL's ring would record and analyze
so the perfected version can be safely used on Zatanna.
Dannered-Zatanna: "
Daddy! You're free!"
[Zatanna glomps Giovanni
Starfire-style]
[insert sound of
bones breaking]
Giovanni:

"
Sweet jebus the pain!"
Dannered-Zatanna:

"Sorry, I'm still learning to control my strength..."