Teleporting within blocked walls?

[NewJeffCT]

If the players were in a situation where they entered a castle where the outer walls were warded against teleport/transportation magics (warding was via a complex alchemical process done when the castle was being built - think gorgon's blood mixed in with the mortar from the stonework from 1E days)... they should still be able to use a Dimension Door or Teleport when they are within the actual castle, correct? If the outer walls are what was warded, it should be okay for them to say, Dimension Door from one interior room to the next, or to have one of them Dimension Door down a corridor and behind the guards to flank them.

Is this correct?

[Shin Okada]

As there is no default rule in 3.Xe core, I say the effect of such warding is completely up to DM. But I can find at least one mentioning on Gorgon's blood in 3e Manual of the Planes.

It is suggested as a protection against entry from ethereal plane. Thus, I guess it is useless against teleportation spells and effects. Because they use Astral Plane, not Ethereal Plane.

Ethereal Plane and Material Plane are coexistent. So, you can make a wall which affects both on Ethereal Plane and Material Plane (like wall of force).

But in case of Astral Plane, it is coterminous to Material Plane but is not coexistent with it. So such a "wall" usually has no meaning. There is no "corresponding places" in Material Plane and Astral Plane.

Usually, to prevent teleportation, plane shift or other inter-planer entry, you must either fill the entire area with some kind of magic (say, Forbiddance) or make a space which is not connected to other planes (say, making a tailored demiplane).

[NewJeffCT]

Originally Posted by Shin Okada

As there is no default rule in 3.Xe core, I say the effect of such warding is completely up to DM. But I can find at least one mentioning on Gorgon's blood in 3e Manual of the Planes.

It is suggested as a protection against entry from ethereal plane. Thus, I guess it is useless against teleportation spells and effects. Because they use Astral Plane, not Ethereal Plane.

Ethereal Plane and Material Plane are coexistent. So, you can make a wall which affects both on Ethereal Plane and Material Plane (like wall of force).

But in case of Astral Plane, it is coterminous to Material Plane but is not coexistent with it. So such a "wall" usually has no meaning. There is no "corresponding places" in Material Plane and Astral Plane.

Usually, to prevent teleportation, plane shift or other inter-planer entry, you must either fill the entire area with some kind of magic (say, Forbiddance) or make a space which is not connected to other planes (say, making a tailored demiplane).

Well, I'm not worried about the mechanics (if Gorgon's blood doesn't work per the rules, then I'll make it something else... umber hulk blood, medusa's blood, eye of newt, or the stomach acid of a troll or what have you).

The way I would look at it is a tall building (a square tower 100 feet tall and each wall 40 feet wide, as an example) has each of its 4 "walls" lined with material that functions as a sort of a permanent Dimensional Anchor. (the spell descriptor says you can target a person or object with Dim. Anchor).

If the PCs were within said building and just the outer walls were subjected to the DA spell effect, would the PCs within the building be able to say, dimension door from the ground floor to the top floor as long as they stay within the building? I would think they could.

[Shin Okada]

Dimensional Anchor does not work like that. But if you don't mind about the mechanics just make it a special feature of that dungeon.

As the DM, you can just claim that dungeon (castle?) is special and no one can enter into nor exit from there via inter-planar travel, but inter-planar travel within the dungeon works just fine.

That is your dungeon and you can decide what can or cannot happen in there. That is an old trick used by good old GG and other authors of official modules (Oh sorry, but this dungeon is a kind of demiplane .....).