The open portal is obvious one-way from the other side. It has all the indications. There isn't an event horizon on this side of the portal that would allow for transport to the other side. So, if the other side is located in Phelix's planar enclave, then there is no way to get there from here, unless the portal can be reversed. Without studying the inscriptions on the walls or the altar itself, there is no way to know for sure. Trying to reverse the portal without the correct planar key could be fatal.
No, more likely the portal is used primarily for scrying/spying.
The magical energy that connects the portal to the magic circle is definitely going from the circle to the portal. The woman inside is a genie. A djinni. An elemental creature from the Elemental Plane of Air. They are typically good but can be very unpredictable, as they are creatures of chaos. The female djinni looks to be in peril from the portal. Her life energy is powering the portal. If the Deaf Knight is truly her protector, then he wouldn't know that the portal is slowly killing her. Vinny knows that if the energy can be interrupted, the portal will disappear. Freeing her will likely dissipate the portal but it could be tricky.
Dispel magic would be needed to get rid of the active
magic circle. She also appears to be in
temporal stasis. One or both of the spells would likely have to be dispelled.
The fire demon that was shown on the other side of the portal is obvious more likely to be an elemental being of some kind but it is definitely a pseudo-natural creature. If Phelix can bring it to another plane from the Far Realm and manage to contain it means either he is very, very powerful or the planar enclave he is using is connected to an ancient civilization that predates Bluffside. Vinny has heard of the Ancients like most citizens of Bluffside. (It would be a Knowledge [History] check to know more than the basics about those ancient peoples, which is on display at the Museum of Sem La Vah.)
That plane is likely very limited in scale. It might have been created using powerful magic (Vinny hopes Phelix isn't that powerful) or even an artifact. For example, the spell
Genesis can create a 180-foot demiplane with one casting, but it also can be enlarged with additional castings of the spell. The spell doesn't create life or construction, but the caster can add such things later.
No, more than likely Phelix discovered a demiplane that already existed and is using it for his own purposes. It could have been created by the Ancients but it just as easily been created by any powerful arcanist or Priest of Creation. If there is a powerful portal that was created on that demiplane then whoever created the plane was/is very powerful indeed.
During his studies, Vinny never came across any texts that refer to a demiplane located coterminous with the Material Plane near Bluffside. Of course, the teachers at the academy aren't perfect people who know everything about The Planes.
The Far Realm is no joke. It is a considered to be an infinite plane of madness that stands apart from the rest of the Mirrored Cosmology (the name for my unique cosmology for Kulan). The plane can transform visitors into gruesome monsters. Pseudo-natural creatures are one type of monster that comes from the Far Realm. Many believe that the creatures known as Mind Flayers also originated there. Those that study the Farm Realm beyond knowing how not to end up there or be corrupted are known as Alienists. (The Wizard Council has divined that Phelix is indeed an alienist.)
Vinny also knows that Sigil is a planar city that is considered by many to be the center of the Outer Planes. It was once ruled over by a being known as the Lady of Pain, but she was overthrown by another powerful being known as the Lord of Agony. Some think that the two beings are actually one in the same, but the Lord of Agony came tp power in Sigil, the planar city changed a lot. Yes, it is still considered neutral ground, but the number of factions in the city has doubled and the creatures known as the dabus, who were once the Lady of Pain's favored servants, are now more like slaves under the yoke of the Lord of Agony. As well, the faction know as the Harmonium have even more dominion over the law of Sigil than they did when the Lady of Pain rules the city.
