28) The Black Thorn. This is one singular thorn of a very hard and very large plant intertwined, cut and knotted into armor. It has the normal characteristics of leather armor. When someone attacks it it releases a spurt of a thick black oily liquid which sticks to whatever touched it (only from the outside, the wearer is safe). The liquid is rubbery and dulls sword blades, makes clubs bounce from hits, etc. This causes -1 to attacks, unless the attacker cleans the weapon used. The cleaning isn't hard, but takes 1 round. The armor can do 10 spurts, after which it has to be submerged in normal water for 5 rounds to replenish its supply.
Oh, and that first hit which causes the spurt isn't yet affected by the attack penalty.