Built a new killbox; originally was going to use the heat of the steam generator there, but that was, well, practically nothing. So tacked on a room with a wooden floor and a bunch of stools.
When these Yttakin raided, I tossed 2 molotovs then set up everyone at the exit. (Spoiler: I didn't need to do that.) Before they reached the first switchback, heatstroke was already setting in. By the time the lead Yttakin hopped another couple of fences, temps passed 200C and they started to get burns.
As they passed the fire room, a couple of idiots charged straight into the flames to break a stool, then walked back through them to resume the sludge through the hallway. Temps reached 700C as the lead Yttakin was finally nearing the end, and fences and even Yttakin started to spontaneously catch fire! All 6 were down.
In the end I captured 2 and added 4 more skulls to my collection. All without firing a single shot or taking even a minor wound!
I know this will be ineffective against mechanoids, but anything short of that seems it won't stand a chance!