There are references to a place outside the Great Beyond,. If memory serves anyways; I've a few questions regarding this place, if it can be called a place.
1. Does it have a name? I've always thought of it as 'the Outside'.
2. What sorts of creatures/entities/ect. hail from this place? (Side question; What Bloodlines/Mysteries/Disciplines/ect. and other Class Options could be associated with this place and its denizens?)
3. Will this place ever be explored, or will it forever remain an off-hand reference?
4. I know there are references to creatures traveling to this place, but is there a a RAW way of doing so, or is that something strictly up to the DM to offer?
If I'm not mistaken, that's where Dou-Bral went exploring - and came back as Zon-Kuthon.
I've only seen it referred to as the dark places between planes or the void between planes.
No real information has been revealed about it at this time, beyond it being where the Empyreal Lord Black Butterly found Zon-Kuthon.
It's completely uncharted territory, so anything happening there will be entirely up to the GM.
We may one day get more info (and learn what actually wrecked Dou Bral), but that's probably way off in the future (if ever).
Eh?
I'm quite sure I read James Jacobs once saying that they are not sure what is on the outside layer of the Outer Sphere, tough he liked the idea that it was the Abyss, up to infinity (I hate the idea, by the way). The inside is just the Maelstrom, with different planes poking around.
If I'm not mistaken, what Dou-Bral explored where the dark spaces between the stars of the Material Plane.
You could, at most, argue that there are more Outer Planes floating in the Maelstrom than the ones we know about, but there's nothing "outside" the Great Beyond canonically.
Of course, as a GM, you're completely free to come up with it.