[phiwum]

Ah, summoning gems! I was trying to think about simple magic traps that could be triggered. Blast Trap is an IQ 17 spell, a bit specialized for what I wanted, but summoning gems could totally work to make a mechanical trap with a magical effect. How to arm and disarm the trap without making it a key in a lock situation which could be easily Knocked? Perhaps a mechanical timer inside the vault, set each night to activate the trap for a number of hours. (A simple timeglass would do.)

Yes, that works reasonably well. Thanks!

Proxy doesn't work for my purposes, since it suffers from a similar problem as Ward. What self-respecting wizard capable of making a proxy would spend his evenings concentrating to detect intruders?

I'm starting to realize that the solution for my immediate problem is simple. The bank should be difficult but nowhere near impossible to rob. It's a small town bank and security measures should reflect that (as should the size of its holdings). I can go with a few traps and reasonably competent guards outside the vault.

Teleporting wizards, however, would remain an issue. I thought about random placement of barrels, thinking that it would make a hazard for a wizard teleporting blind, but the RAW says merely that "You cannot teleport into a solid object," not that you get annihilated when you do so.

Insubstantiality also makes casing the bank pretty easy to do.

And Open Tunnel seems to make expensive, thick steel vaults a cinch to get into.

But, I suppose, I should just accept that all life is dukkha and doubly so in Cidri. When it comes to stuff, the holding is not any easier than the taking. Perhaps the players will cotton to the idea of knocking over a bank, but let's see how long they hold onto their ill-gotten gains.

This capitulation at least makes my idea of the PCs thwarting a party of bank robbers reasonable. Best not to think too hard about broad economic implications.