My idea? Spiritual magic. You learn it from the monks of mooshu.
This magic type would include preperation spells, such as a spell that makes you take -60% damage, -90% incoming/outgoing health and -60% outgoing damage. (pierce does not affect outgoing damage nerf)
or another example
all incoming attacks to allies are intercepted to you, and all intercepted attacks are -60% damage then it normally would be.
these would be like a "second aura" that overlaps the star one, meaning you can have a star and a spiritual aura activated at once.
then it would have special attack spells, doing universal damage, meaning it could take off any shield the enemy has. The attacks would also be split into multiple attacks, similar to myth, meaning if there was a 100 damage spell, it would do 25, 25, 25, 25 damage. Spiritual magic also has a boost on shadow.
My guess would be that eventually Shadow's counterpart school is going to be Light magic. Light creates Shadow, and also destroys it. We worked with the Council of Light to defeat Morganthe and her Shadow magic.
Life, Death, and Myth are already categorized as Spirit magic. For that reason I don't think we'd see another school of magic called Spiritual.