It's come up way to often, You know you've seen it when someone turns Ethereal. "You can't do that." - "Yes I can, Because of X"
Maybe I'm a rules enthusiast, but I'd like an "official" ruling people can point to so these arguments can be ended with a direct to a specific post. I personally haven't (yet) beat anyone over the head with my line of thinking over the topic, but having it come and interrupt the flow of RP is annoying.
Below my own personal beliefs are some quotes from Mr O. regarding the Ethereal pulled from a topic in the bugs reporting section for convenience.
Specifically, there are a few things that bug me if not "allowed", and I understand there isn't a desire to go through the spells and alter things. (and some can't be changed.)
The conflicting sources have only confused things, I've been in several DM events in which things have went Ethereal or Plane-shifted.
Wraiths exist on the Ethereal Plane. There is a wraith floating about in the lower ward. The Foul Old Spirit would qualify as the same.
Bags of Holding are non-dimensional spaces. ( a pocket plane on the astral/ethereal.) Technically you're plane-shifting people and objects every time you open one up. Bad things happen if you rip or puncture one (While inside)
Conjuration. (Orb spells) Are summoned directly from their parent plane.
What I've usually RP'd and what makes sense in my mind is the following:
Ethereal works, albeit in a limited fashion. - No sliding through doors/walls. It also just asks for power-gaming break-ins. (Giving NWN2s limitations, and perhaps the Ethereal Plane has bled into Sigil, just barely allowing incorporeal forms to exist, It
is after all, connected to everywhere.
Plane-shifting works, but is subject to drawing the Lady's attention and "approval" (DM Consent) Perceived threats are dealt with mazes and flayings.
Gate is a no go. - Both in it's planar travel abilities and summoning abilities. Ripping open a doorway to another plane is just begging for an outsider/power that has an interest in Sigil to walk right in and upset balance. You want to gate? Go to another Plane and do it.
Drawing the Lady's attention isn't immediately met with death. (This specific thought is spurred by the events in the game Planescape:Torment , ever go to the shop and have The Nameless One play with the Lady of Pain doll? Yeah, Hilarity) When subjected to her attention. That tingle or chill up your spine occurs, that feeling you know you're being watched and need to tread carefully.
Now for the Quotes by Mr O regarding Ethereal.
wrote: Now this is the option given by Manual of Planes:
wrote: OPTION: WITHOUT THE ETHEREAL
The Ethereal Plane is tightly tied to its coexistent plane. However, you can create planes without Ethereal Planes attached to them. This affects a number of spells, magic items, and creatures.
  * The following spells directly use the Ethereal Plane and do not function if the plane cannot be accessed: chamber, ethereal jaunt, etherealness, ether blast, and Leomund's secret chest. In addition, magic items that duplicate these spells, such as oil of etherealness, do not function in the absence of this plane.
  * The following spells have elements that do not function because there is no Ethereal Plane to affect: dimensional anchor, invisibility purge, make manifest, mass manifest, see invisibility, true seeing, vanish, zone of respite, zone of revelation, and spells with the force descriptor such as magic missile and wall of force. Other elements of these spells function as normal.
  * The blink spell still works, but you have to determine exactly how it functions (if at all) without an Ethereal Plane.
  * Creatures that use the Ethereal Plane extensively, such as the blink dog, ethereal marauder, ethereal filcher, and phase spider are at a distinct disadvantage without access to the Ethereal Plane. Accordingly, they avoid areas that don't provide ethereal access. Ghosts do not exist in areas without the Ethereal Plane.
In the D&D cosmology, only the Material Plane has a coexistent Ethereal Plane. None of the Inner or Outer Planes connect to the Ethereal Plane, so the above rules apply on any Inner Plane or Outer Plane.
Then there's also thing like this added:
wrote: QUOTE
Curtains
Shimmering curtains connect the Ethereal Plane to various Inner and Outer Planes. Just like portals, ethereal curtains create conduits through the Astral Plane. While they can be detected from the Material Plane (with a true seeing spell, for example), ethereal curtains can be entered only from the Ethereal Plane.
Ethereal curtains function like the color pools of the Astral Plane, but they always turn travelers solid when they reach the destination plane (whereas it's possible to project an astral form through an astral color pool, creating a new body on the other side). Travelers stranded on the Ethereal Plane can use an ethereal curtain to go elsewhere. Ethereal curtains are almost always stationary. They are immune to all but the most violent of ether cyclones (see below). Well-known ethereal curtains may be guarded, worshiped, or exploited by those with interest in the plane on the other end.
Curtains can also lead into demiplanes. While a demiplane usually connects to the Astral Plane, one may have an entrance onto the Ethereal Plane. This is common among demiplanes used as prisons, because even if prisoners escape, they're still on the Ethereal Plane, where travel is slow, easily spotted, and sometimes blocked by ethereal solids.
As with any portal, each ethereal curtain can have its own properties. In general such curtains are one-way portals, although there are exceptions (see the ethereal tapestry magic item below).
As with the color pools of the Astral Plane, ethereal curtains have their own colors. The D&D cosmology uses the table below, but you can create your own if you like. The color schemes of ethereal curtains and astral color pools don't need to match.
And this
wrote: QUOTE
OPTION: MULTIPLE ETHEREALS
Within the Great Wheel of the D&D cosmology, only the Material Plane has a coexistent Ethereal Plane. But you may allow other planes access to the Ethereal Plane as well. Some, all, or none of your planes can be coexistent with ethereal planes of their own. You might restrict these “miniethereal planes” to planes of a particular type, such as Elemental Planes or Outer Planes. This means that there could be an Ethereal Elemental Plane of Fire, or an Ethereal Plane of Elysium.
Inhabitants of those planes would be able to access their particular Ethereal Plane and use spells and spell-like abilities that affect the Ethereal Plane. Creatures that call the Ethereal Plane home would be found in the associated Ethereal Planes as well.
An Ethereal Plane connected to another plane may have some, all, or none of the attributes of that plane. It still has the core traits of the Ethereal Plane (no gravity, and a normal time). But it could have, for example, the fire-dominant trait if itÂ’s coexistent with the Elemental Plane of Fire, or a weak evilaligned trait if it's connected to the Gray Waste of Hades. Multiple Ethereal Planes can be used in conjunction with the Deep Ethereal option. In this case, travelers can move from the Material Plane to another plane directly through the Ethereal Plane. First a traveler attains the Ethereal Plane that's coexistent with the Material Plane. Then the traveler moves into the Deep Ethereal, and from the Deep Ethereal moves to the Ethereal Plane that's coexistent with the destination plane.
To make such a trip, use the time scale as indicated for the Deep Ethereal, giving the effort the same time as “returning to the Material Plane.” Travelers coming out of the Deep Ethereal appear at a random location on the Ethereal Plane that's coexistent with the new plane. Finally, you can link multiple planes through one Ethereal Plane. For example, all the Outer Planes might link to the same Ethereal Plane, while another Ethereal Plane links the Inner Planes to the Material Plane.
Yet there does not exist spells such as improved invisibilities, there is 'greater' invisibility, but not improved invisibility. I did check Manual of Planes, Planar Handbook, Unearthed Arcana and Complete Arcane (added with the base 3 source books) for such, but there's none. We're not big on making non-lore custom spells.
Lastly, a lot of spells work differently in the planes... a lot of them. We won't change only few if we do change, we'll add all the planar changes, but it is not major issue by any means and can wait