The spiritual plane is an ephemeral plane of existence parallel to the Main Universe, but does not seem to be a universe in and of itself. Chaos, the French Immortals, and presumably all other immortals live there naturally, and Magus currently lives there as well (though he is trying to return to his home universe). In general, no one in the physical plane of the main universe can sense or interact with the spiritual plane. However, the immortals and any other creatures living on the spiritual plane can see and hear what happens on the physical plane. However, Mr. Verres and his team are aware of its existence, and Sirleck (and presumably most other aberrations) can communicate with beings in it. Those living in the spiritual plane can magically affect characters on the physical plane, and immortals are able to appear in the physical plane as well.
Note that as long as immortals abide by certain agreements, they are only seen when they wish to be seen, which includes other immortals (and other being on spiritual plane).
- ↑ EGS Main Story Comic for 2007-01-12 ("I Also Blame Everything on Space Aliens")
- ↑ EGS:NP Comic for 2015-05-11