is this idea too wanked(or just bad)?

[Lord Revan]

this an Idea for fantasy story I've been thinking.

basically it's an island fort/citadel protected by a fleet of demonic/undead ships that can sinked like normal ship (though they might be abit more durable or pack a bigger punch (or both)), but can never be fully destroyed as long as an item/person/creature in the fort is intact (and/or alive) and will repair/regenerate themselves over time (time being weeks at least) and brust out of the water (assuming they were sinked) to fight again.

the crew of those ships would undead that would be bound to the ship and regenerate with those and be impossible to be fully destroyed the same way as the ship

that thing (what ever it would be) that bounds the fleet to this world would also be kind of an achiles heel for the fleet, mean that destroying that thing would destroy the fleet for good or revert it to just normal warships.

[Imperial Overlord]

It is a workable part of a story, but it is just a part of the story. Whether or not it is any good depends on the rest.

[Ford Prefect]

It could make an interesting antagonist - or even protagonist, for that matter!

[Surlethe]

Is it wanked? That depends. Does your story sound like this --

And then ... oh god ... *fapfapfap* oh yess demonic undead ships oh god *fapfap* unghh kicking normal ship ass ahh *fapfapFAPFAPsploochsploochsplooch*

-- or this?

And then the main characters did interesting stuff and grew and developed as human beings/demons/whatever they are. By the way, the demonic fleet was an interesting experience, but wasn't the centerpiece of the story. The characters were.

It's an interesting idea, but whether or not it's wanked depends on how you write it into the story. For example, the Death Star could have been super-wanked, but instead George Lucas made it simply a part of Luke's journey and growth as a character.