My interpretation of this (and your SJDs may vary) is that Jeff Grubb intended the crystal sphere to be a "reality barrier". If priests can not pull higher level spells through that barrier, into the phlogiston, it stands to reason that they can not pull those same higher level spells through the edge of two crystal spheres into the wildspace in a foreign crystal sphere. This is where the Contact Home Power spell allows a priest to create a conduit that allows them to connect a foreign crystal sphere back to their power source (which is usually a deity, but in this case is a force or a philosophy).Knightfall wrote:Of course, those divine restriction would apply to the native denizens of Realmspace. However, if a force/philosophy priest from another crystal sphere enters Realmspace, there is no way I would rule that he/she would have to pick a god while there. Their power comes from elsewhere. Maybe Ao could block that cleric's power or limit it, but to be forced to choose a Realmsian god likely would go against the priest's beliefs.
We do know that there are faiths that already found in multiple spheres. And we do know that CGR1 The Complete Spacefarer's Handbook explains the process where a priest can spend a year building up a large enough stronghold, with enough worshippers, to create a permanent conduiit to their deity. That process makes a non-native deity into a native one, so it stands to reason that a similar process should allow a priest to establish a philosophy.
However I think that a force should probably either already be in a crystal sphere or already not be in a crystal sphere. And a force should either be something that a deity has taken control of or it should be something that no deity has control over. If you don't have a force within a specific crystal sphere, I don't see how a stronghold full of people that believe in that force, could somehow make it appear. However, we are talking of a D&D universe, where the universe can be re-written to make it impossible to create artefacts, where overgods can turn deities into mortals (and mortals into deities) we are talking of a D&D universe where the world of Abeir-Toril can be torn into two and then recombined into one. So the idea of a force suddenly manifesting on a certain day is not any more "impossible" than those things.
Ultimately, it is down to individual GMs to decide what they want to do in their game, but I think you can infer logic that supports restricting or allowing forces and philosophies.