If they had this much time to make and plan, they should have made a few huge ass pits. Ya, its a lot of work but a good deep pit would be enough to at lest keep one immoble to be stabbed to death, they got enough villigers to do this. As for diging tools, I would use the poor and cute litle turtle shells. This harpoon idea, could work but tis 100's of times harder to pull off as it takes a whole lot of perfect team work plus its directly dangrous. *shrug* but who knows, I am just some bleb.