Gaius has yet another D&D/PS question

[Brother-Captain Gaius]

Aasimon. Specifically, devas. From what I understand, they are divided into three types - astral, movanic, and modanic; each of which can travel a specific subset of the multiverse with utter impunity, but not the subsets the other devas are responsible for (e.g., astral devas have the Outer Planes).

However, certain materials feature said devas outside their realm, such as the astral deva on the Prime Material in Hordes of the Underdark. The deva in question not only made her way there and was later imprisoned there, but was "given a mission" to do so. IIRC she was NG and mentioned no deity, so presumably her superiors were the Five Companions.

This would lead me to believe that:

A) A deva is not restricted from travelling outside his specific subset.

B) A deva has little to none of his planar travelling capabilities outside said subset (as the afore-mentioned astral deva was imprisoned and unable to escape without direct aid).

In retrospect I suppose this was not so much a question as a request to analyze my assumptions - not being a Planescape expert, I thought I would ask those who are.

[SirNitram]

Planescape would make a fool of you, sir; an Assimon can even venture into the Hells themselves(The Deva Spark adventure, a true defining moment in Planescape as a 'More than hack-and-slash setting').

The thing is, the Prime Material is a pain in the ass. Both Assimon and Fiends can get stuck. Other travel in the planes is easier. This is the reason why Primes are so rare out there, and thus so Clueless.

[Cynical Cat]

The Outer Planes are big and the legions of celestials are vast. There are a lot of candidates for its superiors.

IIRC, in general devas travel abilities are restricted to the realms they are associated with. That doesn't mean that there aren't exceptions with more powers, or that portals or magic can't open the way. Especially given how common portals are on Faerun. One should also note that the Lower Underdark is also prone to have portals, especially to the Elemental Plane of Earth and the Plane of Shadow.