So my players just began Book 3 last night, and are at Port Peril, about to have their audience with the Hurricane King. They just now discovered that the throne from the end of Book 2 is cursed (they drug it up from the bottom of the sea with a bunch of effort and magic), and they hit on the idea of giving the throne to the Hurricane King as a gift.
Any amusing (or terrifying) ideas for what happens if he accepts their gift and sits on the thing? (And "He makes his save" does not count as an interesting idea by itself.)
It's hard to imagine a situation where he doesn't have Hyapatia cast detect magic on it first, but hypothetically let's assume that he's careless. Maybe they get him drunk, or something...
The curse makes him desire to conquer and subjugate neighbouring empires, so the first thing to decide is whether he considers himself the ruler of all of the Shackles, which realistically is more of a loose confederation than a true kingdom. If he doesn't, he starts attacking people (such as Bedu Hanji the rakshasa). Beyond that, he's probably interested in the underwater elf city that's been infiltrating his council, or possibly Rahadoum. He'd probably muster all the pirates he could muster and go to war. significantly reducing the number of allies available to the PCs in their fight against Cheliax in chapter six.
Realistically though, he'd get Hyapatia to figure it out first. Once that happened, he'd try to decide whether or not the PCs were trying to curse him (as opposed to just being ignorant) and then react accordingly.
I think he'd be likely to strike against Ilizmagorti and/or Bloodcove to bring two other infamous and nearby pirate cities under his control. "Pirates of the Inner Sea" states that the Hurricane King wants to unify all pirates under his banner in the Mediogalti chapter and pretty much the only thing keeping him from doing so is fear of the Red Mantis. Fear of Aspis Consortium retribution keeps pirates in line in Bloodcove. With the throne causing him to act recklessly, I could definitely see him organizing a fleet to attack one or the other.
It could be interesting in a way, to use the curse of the throne to explain why the Hurricane King let the Chelish invaders get so far along. Perhaps they strike while he is sailing for Ilizmagorti, explaining his absence. If your players like intrigue and secret conspiracies, this could really interest them.
I'd say sit on it. Metaphorically. by the end of the adventure, there'll be a chance to go after the hurricane king himself. But of memory serves, there's no real reason to. Have them giving him the throne slowly make him go mad and try to take Chelliax or something, and if they don't stop him, piracy in the shackles may have become less nuisance, more threat.