Allright, I was looking at the spell Major Creation and had my blood run cold.
The basis of the Midas Meteor:
-Major Creation can create precious metals which will last 20 minutes per caster level.
-Major Creation can create materials by the cubic foot, with one cubic foot per caster level
With me so far?
Well, a cubic foot of gold weighs 1,206 pounds. Roughly.
So, when you get Major Creation at level 9, you can create a five ton of gold which will last three hours.
At level 15, it's about nine tons. At level 20, it's twelve tons. In a quite small volume.
If it were dropped from a great height, the impact would be terrific.
The problem is you can't create conjurations on thin air, along with a 10-minute casting time.
Which is why there's a second part to this.
Make friends with a steamborg or a coglayer. Persuade them to use their steam powers on a Force Generator. Give them the 2,000 gp if you have to. You don't even need amplifiers--the basic 3-foot-disc is enough.
Fly above a city-mech with your buddy. Turn on the force generator. Create a cylindrical lump of gold on it.
Wait for it. Then let it drop onto the mech. Try to center it if you could.
I know the falling damage caps out at 20d6, but, really, I don't think that whoever wrote the falling rules took that into account. That much weight in such a small volume, dropping quite a ways, will punch through just about anything that isn't Adamantine. Especially when you get up to level 15 or above.
And congratulations, you have just made Highpoint history by ruining a city-mech. With two people, a spell or two, and 2,001 gp (a gold piece for the material component of Major Creation. Got to have a bit of what you want to make).
I suppose you could do it to people who were sleeping...But I kinda prefer using it as a plot device. Which killing a city-mech would almost have to be.
It'd only really work on the dwarven and human city-mechs, though, because they're the ones with engines.
And, yes, I call it the Midas Meteor, and it's not that implausible to think of. In a world greatly concerned with materials and metals, someone's going to think of how heavy gold is. And someone's going to know about Major Creation.
Anyway, I've been lurking a while and was working on something for a buddy when that popped into my head and I had to share.