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This question is in partial research for a magical surveillance state inspired from two different sources, Potter and the Natural 20 and Doc Smith's lensman series.

Functionally speaking, there must exist persistent (and preferably un-alterable) records that are not impacted by mind blank. Therefore, characteristics of the surrounding environment are essential for detecting when more rigorous investigation is warranted.

In normal environments, a door is a great "detector" for entry. It has two very clear states "open" and "closed", and does a decent job of forbidding access when closed. (Setting aside other means of getting into the room that have their own countermeasures/detection capabilities.)

However, unlike all the other spells referenced in my answer above, there don't seem to be any useful auditing spells that respond to the environment.

What combination of mundane things, magical items and spells can increment a counter (preferably somewhere secure) every time a door opens and is shut?

Optimally, this solution would scale to all doors and windows in a city. Answers to this should be in paradigm in the sense that they do not rely on items or spells that aren't published in the official 3.5 books.

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Haunted Doorlatches possessed by the ghosts of spiders crying out in the night "Front Door, 1402 Red St".

The fundamental component of this plan is the spell Hauntshift [LM 66]. It translates (its wording) undead into "haunting presences." [LM 6] Door latches will have hairy spider skeletons hauntshifted into them with careful instructions on when to bolt or unbolt the door, when to explode, and when to make noises.

The Latching Haunt

A Haunting Presence has the following capabilities that we're interested in (paraphrased for brevity and interest):

  • Cannot be directly sensed.
  • Bound to objects with moving parts.
  • Dispelled only on the destruction of the haunting object or a successful exorcism which requires 10 rounds of chanting.
  • Bindable to objects from tiny to huge size.
  • Can see and hear up to 60' away, but only normally.
  • They cannot be turned, rebuked, or destroyed while haunting an object.
  • They can choose to speak to "nearby" creatures.
  • They can control the movement of moving parts in the object they possess.

Thus, the first part of the requirements are simple. By creating a special mechanism, a door bolt, mounted in the frame, with sealed bead counting arrangements, and an explosive runes spell, the object is ready to be possessed.

A suitable caster (in this case a Dread Necromancer / Binder Anima mage , purely for tradition's sake and the ability to use fell animate cheaply) will be responsible for a number of doors according to the number of Hairy Spiders (1/8 HD, Monsters of Faerun) that he can animate as skeletons. (Other mechanisms will be available as more cheesy options, but this is straightforward enough.) At low levels, hairy spider skeletons will be moving deadbolts back and forth and physically pushing beads around, but possession is much much better here.

For the sake of argument, we will say that each bead counter has a number of beads, with a ratcheting dropper which ensures that, when the dropper is pushed, a single bead is dropped, and that the device can't be turned upside down. It has whatever structural integrity and auditing spells the casters involved feel like putting on it. In the case of an unauthorised breach (defined as anyone picking the lock or breaching the container in any way), the haunt is instructed to read (even though it can't comprehend) the explosive runes.

Rotation of the appropriate key in the keyway will cause the haunt to bolt or unbolt the latch, and logging the action the with the appropriate bead.

Cries in the night

The other half of this setup is the external audit function. These things are cheap enough (especially as complicated lockwork isn't necessary) that most every (important) door can be bolted with one. More to the point, a network of these exceedingly mindless haunts can be made.

Haunts can choose to make sounds, and can hear in a 60' radius. Thus, a series of dedicated haunts can be used to repeat the sounds they hear. A latch can be instructed to speak during locking, unlocking, opening, "opening but no one is there" events, "housing tamper" and "lock tamper" events. So long as a dedicated language is used, the haunts can whisper to each other inside the thick walls of the apartments, and communicate basic information up the chain to community collecting stations. At these stations, normal events can be logged by haunted pens, reacting according to very simple rules. Unusual events can be ... dealt with.

Fundamentally, since this is detecting the state of a lock and a door, being invisible to undead, divinations, or simple invisibility won't be sufficient to defeat this tripwire, an easy trap for unwary adventurers.

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Any such device you build is going to be considered a 'trap' in D&D 3.5.

I'd recommend looking at the Stronghold Builder's Guidebook. It's technically 3.0 instead of 3.5, but it is the only source I know of for formal rules for building completely custom traps.

From that source, what you are describing is and trap (1,000 gp base cost) with a mechanical proximity trigger (1,000 gp), and an automatic reset (+500 gp), and then modifiers per Search and Disable DCs (+200 gp / +1 increase or -100 gp / -1 decrease from DC 20). Beyond that there really isn't much to the 'trap' as you don't want it damaging anyone.

That's the mechanical version of the trap. How it response to entry / exit is probably just a simple bead counter similar to what is used in old gum ball machines.

If you are interested in third-party resources, I'd also suggest the Traps & Treachery series of Legends & Lairs from Fantasy Flight Games. (Fair warning, it may be out of print by now.) In particular Traps & Treachery II contains a trap called 'Room of Cunning Observation' which is very similar to what you want (though not exactly the same). Included with this one is the mention that the primary difficulty for rogues trying to search and disarm traps is even telling there is anything there to disarm.

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  • \$\begingroup\$ Is there a method of determining when such a trap has been disarmed? (Hopefully one that is not itself a disarmable trap.) That would turn this into a mechanism that at least lets the city know when there's somebody in town messing with things. And then Hindsight probably comes into play... \$\endgroup\$ – doppelgreener Nov 24 '14 at 8:16
  • \$\begingroup\$ @doppelgreener What do you mean by "method of determining" here? I mean, if one of town guard goes thorough the door, and other sees counter not increase, they know it was disabled, right? \$\endgroup\$ – Mołot Nov 24 '14 at 9:33
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Use Enormous Amounts of Photostatic Rock

The magimorphic rock photostatic rock (Underdark 105) has a unique property, in that

Events that happen in the presence of this rock imprint upon it for a short time. One cubic foot of photostatic rock picks up impressions in a 10-foot radius and automatically relays them to anyone who touches it later. The effect is similar to that of a stone tell spell, except that the photostatic property reveals only what happened within its radius in the past hour. Every additional cubic foot of photostatic rock provides 1 more hour of memory and expands the radius of sensitivity by 10 feet. A photostatic rock records only what it witnesses (treat its perspective like a burst), so it cannot record what goes on beyond a closed door.

The only real problem--at least, from a player's perspective--is the lack of weight and price for photostatic rock, but the 4th-level Clr spell stone metamorphosis [trans] (Und 61) et al. permits instantaneous creation of large amounts of it. The spell specifically mentions transmuting the magimorphic rock crumblestone (Und 104-5) into granite, making transmuting magimorphic rock an expected outcome of the spell.

This leads to some weirdness. Mandating every building's foundation be photostatic rock means banning rugs and perhaps requiring everyone sleep in hammocks, eat off glass tables, and use lawn furniture indoors. Mandating every building's ceiling be a photostatic rock slab means the city's architects are, possibly, geniuses (depending on the DM-determined weight of photostatic rock, of course), and the authorities are even more icky than initially envisioned.

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  • \$\begingroup\$ Why not non loadbearing walls? \$\endgroup\$ – Brian Ballsun-Stanton Nov 24 '14 at 12:33
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    \$\begingroup\$ Floors or ceilings are much harder to circumvent accidentally. \$\endgroup\$ – Hey I Can Chan Nov 24 '14 at 16:49
  • \$\begingroup\$ I actually really like this because it induces all these side-constraints upon the civilization that will give it a distinct character, rather than just functioning as a complete drop-in replacement for ordinary doors. \$\endgroup\$ – Grubermensch Dec 6 '14 at 3:34
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I don't have a copy of the epic magic rules in front of me, but I don't think this would be too difficult to pull off with an occasionally-renewed epic spell, especially if it relied on a kind of "central console" as a focus that the magocracy actually kept the physical counts at. "Harry Potter" style beads could be used as counters, or tally marks on parchment, whatever you wanted. Magic mouths to announce if a door or window is opened without being unlocked or a password being spoken, whatever. Epic magic is intended for ridiculous huge spells with multiple effects.

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Can you build a counter (mundane or magical) that triggers off of an electrical current being interrupted? If so...running a current from the hinges, through a wire inside the door, to the striker/latch could be used to trigger the counter. This has the advantage that any Rogue who comes across this setup wouldn't have any clues that'd tip them off as to what's going on -- they'd either need to sense the current through the door/latch-to-striker voltage, or to dissect the door and find the wire inside it.

Likewise, current generation could either be accomplished through a hidden electrochemical cell (voltaic pile) and carbon block, or by enchanting some object with a small spark/electricity cantrip as the currents required here are rather low anyway, to avoid giving someone an electrical nip if they accidentally put themselves in the circuit.

(BTW: I measured the hinges and striker on my bedroom door with a Fluke 77 III DMM: the hinges were ~500ohms to 1kOhm and the latch+striker <100ohms after making solid enough contact to break the surface corrosion/varnish -- this is more than enough continuity to allow a small current to flow.)

Unfortunately, though -- there's a RAW problem going on here (as Miniman and Grubermensch pointed out to me on chat), and that's the "disarm traps" mechanic can't be wrangled into modeling clever stuff, apparently?

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  • \$\begingroup\$ If you can annotate your answer in paradigm to show a) how which spells can generate constant current for any useful length of time, and b) why this wouldn't be subject to the normal disarm traps mechanics of the rogue, this would be a much better answer. \$\endgroup\$ – Brian Ballsun-Stanton Nov 24 '14 at 4:23
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    \$\begingroup\$ Voltaic piles have been known since antiquity -- and I suppose a constant-current spell at the mA level (albeit not something I know of offhand) would be small enough to be considered a cantrip that then could be enchanted into an item -- surely, if Shocking Hands is first level and capable of doing significant touch damage, a current below the threshold of notability for humans would be far easier for a spell to generate. \$\endgroup\$ – Shalvenay Nov 24 '14 at 4:29
  • \$\begingroup\$ As to "disarm traps" -- how would the rogue disarm a trap he cannot perceive the presence of? \$\endgroup\$ – Shalvenay Nov 24 '14 at 4:30
  • \$\begingroup\$ @Shalvenay There's a lot more to perceive the presence of here than just the electrical current. There's also every piece of the mechanism that carries and utilizes that current. \$\endgroup\$ – Matthew Najmon Mar 6 '15 at 17:33
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Similar to Shalvenay's answer (as in, an undetectable "trap"), but far more mundane...

Have a button next to the hinge that is compressed when the door is shut, and springs up when the door is open. If it is between the hinge and the door stop (refer to diagram below) then it should be undetectable from either side when the door is closed.

Diagram of a door jamb

Have the button connected to a sliding rod with a hole in it just big enough for one ball (marble, ball-bearing). Have a chute above the closed position containing numerous balls. Have a second chute below the open position that leads to the "counter" container. Count the balls in the container to determine how many times the door has been opened.

Note: This breaks the intent of a Rogue's trapfinding ability, but realistically there is no way to find or disable the button while the door is closed.

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    \$\begingroup\$ Except, y'know, rolling Search followed by Disable Device. \$\endgroup\$ – Please stop being evil Jan 26 '15 at 10:12
  • \$\begingroup\$ @thedarkwanderer If it is hidden as I describe, then realistically, no amount of searching will make it visible. If you want to ignore realism to maintain game mechanics (or you think Trapfinding is some kind of supernatural sixth sense), then the Search roll should be against a very high DC. \$\endgroup\$ – Adeptus Jan 27 '15 at 0:15
  • \$\begingroup\$ Also, the way these work would have to somehow be kept completely secret, despite the buttons suddenly becoming not so hard to find when the door is opened. (And it only takes one brawl putting a hole in the wrong spot on the wrong wall to reveal the entire mechanism.) Once people know these are in play, and once security-expert types know how they work, it becomes trivial to use divination-guided telekinesis abilities to run the mechanism in reverse, cycling it while forcing the balls through backwards, or just open up the walls, arrange the balls as you like, then spells to rebuild the wall. \$\endgroup\$ – Matthew Najmon Mar 6 '15 at 17:31

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