Any creature that touches the babau, or hits it with a melee attack while within 5 feet takes 4 (1d8) acid damage. Any nonmagical weapon made of metal or wood that hits the babau corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made of metal or wood that hits the babau is destroyed after dealing damage.