“A special spell is required because most Intellego spells are designed to be subtle, and they are more subtle at higher levels.”
DE p.370 Masking the Odor of Magic
“Prevents the detection of a magic spell, or of a magic power in an item or being, by InVi magic, unless the level of the InVi spell exceeds twice the level of this spell – 5”
Would it be reasonable to think that if most intellego spells are designed to be subtle, thus requiring a special spell to detect them and become more subtle at higher levels that a PeVi spell, designed to hide magic, would also be designed to have the same qualities?
I find it un-elegant that MtOoM effectively hides an effect but fails to hide itself. It feels like an invisibility spell would make the target invisible but the effect itself would glow… which I think is a canon description of a fatal flawed spell.
My hypothesis is that MtOoM would not reveal itself to the likes of Sight of the Active Magic. It might be giving itself away to the Quasitor’s Intellego Mysteries but otherwise would require a specific spell that scrutinises for hidden magic.
The spell makes no sense if it does not mask itself, so it is also masks.
The spell masks another spell. A magi can tell a spell was masked, but not which spell, so it has a purpose. Also, why would it mask itself? Because it’s a better spell? Just because a spell has limited purpose, does not mean it should use different rules.
I lean towards option 2. I think a magi could create a new spell with +1 magnitude for complexity, and have the spell mask itself also. The +1 is a vague suggestion. Some SGs may suggest higher.
This version of the spell is vastly superior to a version that is not masked. To the point of making the lesser version irrelevant.
I think we can assume that all ill intended Magi design the effect to mask itself and the only reason the order hasn't mastered an effect that is more powerful than it ought be (via experimentation), is because it is a borderline illegal spell designed to fool other Magi or Guernicus.