As an aside, the damage inflicted on you after a rest, if you aren't fully healed, is magical damage, not positive damage.
I figure it's worth mentioning because I think both of these types of things are trying to inflict un-resistable damage. I'm not aware of any way for PCs to get Magical damage resistance, but some NPCs (and possibly MPCs) do have some. (I think Dry Liches have, for example.)