If you convince the spiders to attack, they will attack goblins in the main hall (Gut's area), but they never move far enough to trigger the other bosses. Of course, that also makes Gut attack you, the goblins go for the war drums, etc. It's basically a way of kicking the Gut fight off with a couple of allies. You can probably pull attackers from Ragzlin's area to them, but I haven't tried that. You can definitely leave them caged up and push goblins into their pit, but you have to pull the goblins close enough.
The guy is actually alive the first time you enter the temple, but it is a timed event, so if you wait too long they push him in and walk away. I keep meaning to see what happens when you dialog with them, but never remember to go there first.
