Shadow Cache

[Ruethgar]

If you cast a Transdimensional [Shadow] spell with your hand in a Shadow Cache, do you gain the extra reality from casting in the Plane of Shadow?

[tiercel]

I think, taking Transdimensional literally, that the feat only allows spells from the Material to affect the Ethereal/Shadow/extradimensional, not the other way around. So if the spell actually happens “from” the Shadow Plane (despite only your hand being there), Transdimensional doesn’t let it affect the Material; if the spell originates from the Material, then it doesn’t actually gain the benefits of being cast from the Shadow Plane.

If you rule that Transdimensional Spell works both ways you have a bigger can of worms — spellcasters on the Ethereal/Shadow utterly own everyone that can’t return fire by immediately shifting to the correct plane or spot and target their attacker and use Transdimensional themselves.