There is a material called "blood" that was used in an old system to make a certain kind of enchanted arrows "blood arrows". Not literally blood, but it would invoke a bloodcurse sydrome. It's designed to melt at body temperature and impart a syndrome. This is from before itemsyndrome etc. was useable for arrows.
I think there are no reactions for it any more, but the material is still in the raws. I doubt invaders are really supposed to be bringing it, but it is tagged [WOOD] so if you are playing one of the versions where Elves don't have mithril, I could imagine them grabbing it. But it's a pike, so i dunno why elves would have it either.
