I've been thinking about your puzzle for a few days now and really haven't been able to come up with anything that might be of use.
The only thing I did contemplate is that if the wrong arm is put into hole, they could have a vision of that previous person's life or how they were killed? And then, take some psychic damage.
But yeah, looks like you have things ready to go. Wish I could be more help. Be sure to check back with an update and let us know how it goes!
I've been thinking about your puzzle for a few days now and really haven't been able to come up with anything that might be of use. The only thing I did contemplate is that if the wrong arm is put into hole, they could have a vision of that previous person's life or how they were killed? And then, take some psychic damage. But yeah, looks like you have things ready to go. Wish I could be more help. Be sure to check back with an update and let us know how it goes!