Astral Harpoon

When fired from a ballista or similar firing mechanism, this harpoon has a +3 to attack and damage rolls and deals 6d10 piercing damage instead of the normal amount of damage. When firing this destructive harpoon, if you roll a 20 on your attack roll against a non-magical ship, you cause catastrophic hull damage that causes fractures and breakages to compound. For the next minute, the struck ship suffers 2d10 at the end of each round.