Understanding Mystic Portal Physics

[Talavar]

A few things:

- For passing through solid surfaces, the mystic portal can be up to 12' per level: if you only want to pass through a 2 foot thick wall, it can still do it; you don't end up 120' inside the building past the wall you were trying to bypass.

- For both teleportation and passing through solid surfaces it is a one-way passage. The one-way passage phrase must apply to them, because on its own, the phrase doesn't refer to anything. From the casting side, you can see & pass through the portal. Once you've passed through it, or to people at the other end/side, there is nothing to see/interact with, and to people at the other end, anyone/thing passing through the portal appears to come from nowhere. The point of origin doesn't disappear, just access to it from that end of the portal doesn't exist. For the duration of the magic, more people could come through the mystic portal behind the caster, but no one can go back without a separate casting.

The TW hull-breacher missiles aren't good support of you 2-way corridor interpretation, because TW devices regularly tweak the incorporated spells' standard effects, and I would argue that that has been the case here. How they function invalidates the 'one way passage' portion of the spell description. That's fine for a TW item - their whole reason for being is to alter spell effects - but not evidence of how a standard casting functions.

[glitterboy2098]

i've generally assumed that the Mystic Portal in 'walk through walls' worked sorta like a straight line version of the portals from the eponymous game. a circular rift opens up on the wall/object in front of you, and another opens up on the otherside of the object. the spell never mentions a "tunnel" specifically, after all.

this also matches up with the 'teleport' option, which basically just opens up a hole between two points you step through.

[Tor]

The only way it's workable in my mind is that yeah, a mystic portal is another temporary dimension. That's probably why it's (I'm pretty sure) lumped along with temporal magic sometimes.

If you take a look at the "Passage" spell in Through the Glass Darkly, it works similarly, cept it has sentience, and indefinite duration, and no range limits.