I... Am... A.... Robot...
*** Queen of the Demonweb Pits SPOILERS ahead ***
That giant spider mech at the end of Queen of the Demonweb Pits was crazy. It was the kind of thing that can make or break a campaign. I'm sure lots of groups really dug the way it changed the game, but I'm equally sure others can say their campaign started to fall apart when they found the spider robot. It was incredibly cool, but did it really belong in AD&D?
This mech might stalk the blasted plains of your campaign. Maybe it's the secret weapon of the local Baron? Maybe it's a tool of the Orc hordes, imbued with the soul of a fallen hero. Maybe it's the party's toolin' ride (just try fitting it into the dungeon, though).
The robot dungeon is inspired by the art of Scott C, whose artwork seems to be popping up everywhere for me lately. Scott draws these crazy environments full of little characters living their everyday lives. That's very dungeon-y to me.