How would you secure a steampunk bank vault?

[Micp]

Hello. I'm co-mastering a homebrew scenario based on the pathfinder rules. The setting is American civil war meets fantasy meets steampunk. The group are six 4th level characters that are going to break into a bank vault containing the blueprints for a gatlin gun that shoots chain lightning.

So what should stand in their way? we've talked about stuff like electrical traps and alchemical golem guards (scaled to meet the appropriate CR). magic should be kept to a level that can be explained by "steampunk sciency stuff"

other stuff they'll encounter are cyborgs with steampowered grenade launcher arms, labs with giant amoebas and shocker lizards and xorvinthaal dragons in the form of thomas edison and nikola tesla fighting on either side of the war (thomas edison is on their side - the south, and nikola tesla the other. tesla is the one who designed the gatlin gun, and the final encounter is breaking into his lair. he won't be present).

Thank you for your suggestions

 

[TheAuldGrump]

Hmmm, I would start off with a pair of time locks - one on the vault itself. Make the timing mechanism big, shiny, and obvious - perhaps an enormous hourglass, fastened to a geared wheel. When the sand runs out the wheel turns, resetting the hourglass, the vault remain unlocked for that same amount of time.

A grip allows the clock to be reset manually, but only while unlocked.

Inside the vault are several higher security pillars, that open like old fashioned mailboxes. They are socketed into the floor on pistons, and require two keys to unlock - and that lock is linked to the timer mentioned above.

For the security bots... perhaps a frieze? The security bots looking like a shiny mural of stern looking men, keeping them out of the way and looking decorative at the same time.

If the bank is really twitchy, perhaps there is poisonous gas inside of the vault when the door is locked? Cycled out when the great wheel rotates, and a careful listener can hear the hiss of the gas at it cycles either in or out.

The Auld Grump

 

[Glade Riven]

If you can find it, pick up some Iron Kingdoms d20 stuff. It's getting harder to find, though..

How about a steam golem built into the door itself? You can't open the door without first defeating the golem...or having the right credentials. A shotgun/wand spell trap for those who open the door improperly would be cool, too.

 

[Herobizkit]

How about a steampunk variant of a DNA scanner? The lock requires a drop of blood from a specific person before it will even display itself.

Next, the lock itself should be some kind of puzzle. How about messing with the players and make it an abacus? The combination must be entered by arranging the beads in correct sequence.

Finally, once inside, nothing says magic like a Treasure Golem. They will have to fight their gold to win it.