There is never an orc.
There are always orcs.
Within the belly of each is a burning nugget of iron. Carve off a limb and embed a slug of iron. Wait a week as muscle forms, cramping in agony around a splinter of white-hot pain.
Their black blood ruins metal, corroding it beyond repair. Arms and armour used against them will be useless in 3 days.
Left in the Sun, they die in hours.
At night they slink from the mountains for meat and metal.
HD 1 / AC as Armour / Damage as Weapon