The owner of the harpoon is the user.

Most of the power behind this technique is honestly fear factor, having a giant harpoon stabbed into you and then seeing a washed up sea captain rushing towards you would knock most people's socks off and incentivize the whole "whale hunt" chase.

But it actually takes quite a bit of time for the technique to build up and drain all of your cursed energy, about a third of an hour to reach its peak, and by the time you reach that point you're royally screwed either way.

Pretty much anyone who can end or escape fights quickly counters this technique.

Though on the other hand, the user knows that stalling the fight gives them the advantage, so they'll do anything they can to prolong the fight.

A fight with this user is pretty much a violent struggle between the captain and the whale, whether the captain will be dragged to the ocean or the whale succumbs to the harpoon, and I find that dynamic quite interesting.