I propose we replace the current delayed instant passwall effect with a multiple stage process, inspired by rock worms. In the most basic implementation, you'd spend a regular turn casting next to a wall, an AC boosted turn passing through, and a regular turn to come out the other side and revert to normal. Three turns for your basic geomancy passwall that is found in a book of geomancy. Given the reduced vulnerability, it might need to be slower (or you move at half speed). For deeper walls you might spend some time deep in there immune to attack, therefore some consideration would be needed to prevent a tomb of doroklohe situation, moreso with the second version I suggest below. You would not be able to change course in this version, you would select a direction like the current passwall.
A more complicated, perhaps higher level variant would be a rock worm form with corresponding vulnerabilities and one catch: it must be cast adjacent to a rock wall, must be ended adjacent (or inside via duration) to a rock wall, you can end it with an ability gained, or have it painfully end (halve health) if you do not have any rock wall adjacent to you. — lordsloth 2010-06-11 16:26
How would this work for stabbers? — rob 2010-06-14 11:35
Passwall actually is quite useful, so much that I often recommend passwall before stone arrow for non-elves. Practically similar to teleports, monsters will lose track of where you are, without the random destination - this can be very powerful. Paradoxically, more power is less tactically useful - greater depth means being locked vulnerable in place for longer. It's like taking off armour in an attempt to escape. There are potential conflicts with other delayed effects - reading a scroll of teleportation and then casting passwall will result in you teleporting to a random location and then instantly going back to where passwall would have taken you.
The passwall/teleport interaction you describe sounds like a bug – would you mind filing? — rob 2010-06-14 11:33