Gravity. You win a lvl 1 hireling.
Is it possible to either "prevent" the members of the ambush from falling down the shaft or maybe adding an electronic tag on them so we can track them down more easily? It's really hard to find which ones are the ones that are ambushing us instead of the ones that..well, we ambush. Maybe make the ambush monsters different? Or maybe my first suggestion actually, giving them something to be happy about, give meaning to their lives, so they won't feel the urge to jump down into the void.
Oh, and if you are thinking "why didn't you kill everything on your way up", I could find a thousand funny, rude, or condencending responses, but I'll just say NO
Thanks for reading