Hello,
The 12th house does not swallow the status of Jup. Or, well, the world we live in, let's call it the real world, things sort of go below the surface in the 12th. If a chart does not already have an active Nep or Pisces type quality, almost anything happening over the 12th can be fairly 'unsettling'. For e.g., for earth and fire signs, this can be a very difficult transit to take. The reason is that in the 12th house the subconscious takes over the conscious (or what we may like to call the real self).
The conscious self is 'tangible' if you like, but here the intangible/the hidden self is what the native is confronted with and cannot understand. The original quality of Jup is to expand and that is exactly what it does even in the 12th, expanding on the subconscious. When planets roll over the 12th, they knock on the door of the subconscious, our hidden self. Finally, we are forced to let it surface, but are not used to it, so feel even more disillusioned, ever fearful. The 12th house has a very fluid-like quality (something you can't grasp) to itself, and Jup is only expanding on it, so yes, it may feel like being engulfed by the unknown.
In Western Astrology, Jup in the 12th house is like that hidden (12th house) angel (Jup) that is said to save you from the hidden enemies (another quality of the 12th house). Another thing that Jup on the 12th can do is make you more aware of your innerself/your soul (things that don't happen in the real world). It is a time to finally retreat, take time away from the 24X7 routine and introspect, sort of like hibernate for some time. Finally, this transit may also make you sleep (12th house) more.
AQ7
