The Septic Skewer is a Post-Moon Lord Sulphuric-themed ranged weapon similar to the Harpoon that is dropped by The Old Duke. It automatically fires a harpoon that infinitely pierces and is unaffected by gravity. The harpoon travels a long distance before returning to the player, releasing bacteria particles on its way back. Both the harpoon and its bacteria inflict the Sulphuric Poisoning debuff.
Its best modifier is Unreal.