A and B are cave-in traps. The first killed around 20 and the second 15 or so (they was a bit scattered).
C actually is all it's needed to kill them. Upright spikes connected to a lever on repeat. 10 iron spikes per trap. Copper in the first part of the second corridor, but they didn't make it that far.
With 7 still alive, I stopped impaling them, to actually see some combat, wich leads to:
D, a cage with 40 war grizzly bears. They managed to lightly wound most of the clowns (with some serious wounds on a couple), but got slaughtered pretty quickly.
Puppy is a puppy, so there's something past the bears to give them a pathing target when the drawbridges are closed.
E is the station point for my infantry (5 legendary hammerlords with spoilerite armor and 5 legendary swordwarves with spoilerite armor and swords). They did pretty well against 7 clowns, with only one dwarf seriously injured and all the others barely scratched. Severe spinal damage on the one injured, I think. Had to retire him.
F is the station point for marksdwarves behind fortifications, but I didn't fight in front of them. I fought in the bear room to save the idiot who went to pick up the only unforbidden demon testicle in the entire level.
At the bottom, near che central stairway, there's a 3-deep pond of water to wash away all the potentially dangerous shit like extracts, dust and the likes.
All in all, pretty disappointing. Just fill a hallway with spikes and impale them.