Due to recent events in my Saga, the Covenant of my players has now been transported to the third level of a magical regio. They would like to invent a spell to allow seeing through regio boundaries directly from the third level to the "ground" level. What kind of effect would you suggest?
Rulebook p. 158 suggests InVi, Base Level 3 : "Detect regio boundaries. If cast with a Vision target, this provides enough information to find a way between levels, for regiones that allow that sort of entrance. Otherwise, it reveals the presence of a regio, and possibly its rough shape."
This is all very well, but the intended spell does not exactly fit this description, since my players are not interested in detecting regio boundaries themselves, to see beyond them. Any idea of the required spell level?
ArM5 p.158 InVi 20 'Piercing the Faerie Veil' uses the Guideline you reference "to see through the boundaries of regiones". So seeing through two boundaries at once might warrant another magnitude perhaps?
The ability of spells to work through different layers of a regio has been left undefined. On one hand there is no rule that says that magic doesn't work through regios, on the other hand situations where magi become trapped within regios (such as the covenant in Lion and the Lilly) become much harder to justify if charters can cast spells to anything they have an AC to. I've (for the last decade or so) made the decision for my games that it depends on the regio and I'd love to see this written into the line someplace but to my knowledge it hasn't been.
That being said the ability to see through a detected boundary seems like it won't mess up anything. The ability to see through multiple boundaries may mess something up (but nothing in particular comes to mind).
I'd make up a guideline for intellego imaginem (vim) and make sure that the final spell is a bit more difficult ( a magnitude or two) than piercing the faerie veil when I'm done.