I want to identify a structural problem.
Who are the elves fading in comparison to?
We have (a) insect mercs, (b) parasite pirates, (c) ancient isolated snakefolk, (d) racist rebels.
Where is the rival power? Or is it an internal rot?
Like, the elves have run into their reproduction rate problem. They are crazy powerful, but each high wuality elf takes more than 100 years to product, and they come slowly. Even elven grunts take 50 years.
The dynamic "grasp the world" elves have been getting killed off. More and more of those that survive are paranoid, lazy, passive and/or reclusive.
Conflict between half-elves and purebloods, caused by the purebloods being insanely powerful (100s of years of power collecting and expertise), while half-elves able to reproduce faster and grow up quicker, is a fracture in their society.
A solution a pureblood line has developed is to use mercenary insect warriors instead of half elves, under the cover that "even half elven lives are worth saving".
Until recently, that internal rot led to the pirates freeholders growing in power. Once upon a time they where pirates, but now control key supply locations, settlements, and charge tarrifs on cargo. Those who do not pay the tarrif are preyed upon.
The previous rlven administration decided it was cheaper to pay rather than fight; the new administration ceased payment of tribute. This caused an initial setback on elven trade, but the new insect mercenaries and capital ships changed the game. But there is a very limited number of those (like 2-4).
In turn, the Knights represent a nominally non-connected force to a rival weaker than elven empire, but actually get resources from them. They have been providing the pirates with supplies to build anti-capital ship techniques (avoid? sink? outrun? - I like avoid, mainly). They have a weapon capable of sinking a capital ship, and are trying to set up a situation to use it (ambush).
The elves, meanwhile, are demanding no nation pay tribute to the pirates; many do in secret, including elven merchant guilds. Others do not. The pirates aggressively go after people who don't pay the tax, and horror stories of not paying is important to bring more online. Their ships don't guard other nations cargo.
The Snakes can be the weapon dealers of the resistance. They sell the stealth magic, which is fueled by mortal souls, as well as the knight's capital ship weapon (maybe it summons a shadow sea serpent that drains the life of the crew?).
Goals:
Elves want domination.
Pirates want the elves to pay tribute. And will engage in terror tactics to pull it off. They want that ship killing weapon; one wants to use it on a mainland elven city.
Knights want to weaken the elves, or make their empire fall. This could permit their mainland kingdom to dominate the elves.
Hive wants the elves to become dependent on them, then overthrow them in a decapitation strike.
Snakes want to ammass enough souls to unkeash a mega version of the weapon, and kill all of the warm bloods in the area, so they can continue in peace.
Fanatic Knight has figured out what the Snakes are up to. And wants to steal the weapon and unleash it on the elven homeland, wiping them all out.
Hive may figure out the weapon; it being genus specific means they could use it against the snakes and the mammals.
So that permits everyone as a possible BBEG. Except the elves, who are patsies.
