Magic is life and life is magic. Every soul radiates energy, forming an aura around itself that prevents astral intrusion and repels parasitic spirits. Wizards call this natural shielding effect the parma magica. This unseen mantle surrounds every ensouled creature and every object imbued with lasting magic, warding them against direct magical manipulation.
Think of your aura as an invisible yet iridescent bubble, quite slippery to the touch of spellcraft and extending slightly beyond your body, also enveloping body cavities, clothing and what one "attends" and carries close. Magic that tries to manifest inside of your aura will be shunted just barely off target.
Basically:
- A wizard attempting to teleport a rock into your body (or vice versa) will find it materialized harmlessly beside you.
- A portal closing on your torso will shove you outward rather than slice you in half, unless it is physically impossible to be shoved.
- Being inside an object when a spell of intangibility ends causes you to be pushed out and take damage as if you had fallen that distance.
- Hydromancy cannot freeze your blood, telekinesis cannot pinch a vein in your brain, fireball cannot be evoked directly in your stomach, etc.
Breaking parma magica requires extraordinary power and/or magic specifically designed to pierce and latch onto auras - infamous among these are the feared soul-curses. Even then, such sorcery must burn through the aura, a costly and dangerous feat. Thus also the fireworks that are war magic: It is far easier to hurl fire, lightning or poison - manifestations with physical presence - than to weave a complex curse and still pay a hefty mana cost. Biomancy, whether medical or polymorphic, also suffers from this natural ward and often demands physical contact, allowing the caster's aura to mingle with the patient's. Even then, the process is draining, laborious, and often unstable.
Note that auras only protect the ensouled and the ensorcelled - mundane objects can be transmuted or telefragged without significant resistance. (Undead and constructs are usually soulless but ensorcelled.)
