The harpoon is a heavy throwing spear with a barbed point that comes off when it is thrown. A line is fastened to the point, and used to reign in the prey. If the prey is too strong, the hunter might be dragged olong or forced to let go of the line, but the woubd might still prove fatal and the rope still facilitates retreiving the corpse.
In order for the hook to stick to the target, you need to score some damage. For each Wound Point you scored, you get a +1 bonus on all competitive Strength rolls when ytying to reign in your targhet, and if your score a higher, the harpooned target suffers the Outcome as WoundPoints.
A harpoon is a hunting weapon. It works best against animals - an intelligent creature can dislodge the barbed point with Medicine, Healing or similiar ability. Or the line can be severed - a rather simple task.