First, some quotes from the relevant verbage:
Rego Vim Guidelines
Opening the Intangible Tunnel
Alright. That said... I am still left wondering what the exact limits of the use of this type of effect are.
It seems pretty clear that one could, for example, cast a mentem spell to implant a suggestion through this without a problem. Fireball directly at the target of the tunnel, no problem.
Now for a couple of tricky ones.
Presume that the caster has an Intellego Imagonem or similar effect to perceive the other end of the tunnel.
Fireball targeting not the target of the tunnel yet something in it's vicinity. This I'm not sure about. The Tunnel spell description says that another caster can use the end of the tunnel for it's range to the caster. Could not the caster likewise cast, with supplementary perceptions/senses, through the tunnel at a different target using this same range mechanic?
A Rego (Whatever Form You Please) effect to instantly transport something, say, fifty paces. If you have a Tunnel up, and you are 'touch' range to the end-point... why couldn't you start your fifty paces from the tunnel terminus? Or likewise hit a target with a low-magnitude, short distance-moving, high penetration rego corpus to pull them through the tunnel to you?
Basically the question is to what extent does the 'conduit' effect of Rego Vim manipulate Range? The description says 'any spell of greater than personal range' ... yet also 'on that target'.
Theoretically, especially since it allows spells to flow both ways, this seems a 'wormhole' effect for spells/magic in general. It seems logical to me that it would allow for the bending of ranges through the effect as well, yet I'm not sure if the verbage supports the idea.
Personally I'm inclined to say it should either not allow backflow ( i.e. simply establish 'arcane connection range' to the target for another supplemented spell ) or, work as a 'wormhole'-like conduit for magic as I described... for consistency.
Thoughts?