"Only a fool would believe he knows the deep from just what he sees on the surface."
The Scrapsea, as this world is so lovingly called, is comprised mainly of water and scattered archipelagos. The vast majority of residents live on a worryingly small number of islands, and other brave souls have struck out on ships to form colonies amidst the waves. Centrally located amidst the isles churns a vicious whirlpool, one comprised of near-black water and seething foam, and it kicks up a thick, dark fog that has polluted all the land in its immediate vicinity, slowly making its way to the corners of the globe. This phenomenon, known as "bleak tide", has had a poisonous effect on everything in its path. Once thriving port towns have crumbled and become home to shambling abominations wrought from organic creatures that have succumbed to the fog's toxic influence. The oceans now ripple with the tail strokes of enormous sea beasts and nigh uncrossable storms go hand in hand with the bleak tide. Little is known about its origin, and though its effects are quite clear, cures seem impossible, and side effects range from physical corrosion to mental debilitation and insanity. Often, they come in pairs, leading to the hordes of psycho raiders who inhabit the innermost islands with their twisted forms. In rare cases, small doses of dark water have been known to be almost beneficial. Some manage to escape with just the right amount of insanity, enough to make them fearless in the face of danger and seemingly able to disregard the laws of physics in battle, using weapons seemingly much too large for themselves and moving in such a way that any sane person would assume might paralyze them. Others showcase abilities akin to what the old books might even call "magic", though the exact extent of these stories is questioned heavily. Brutes with the ability to hurl fireballs, as told by drunken privateers? Not the most compelling proof.
With such a virulent and inexplicable plague as the bleak tide, spreading day by day as it were, the Scrapsea's society has evolved to mirror its surroundings. Any settlements that manage to blossom into towns or semblances of cities are full of hardened sailors, scrappy pickpockets, crooked gamblers, ruthless mercenaries, and, of course, off-kilter treasure hunters. Sure, the world's gone to hell, but that doesn't mean that there's not still valuable out there to hunt down. As more and more islands succumb to the tide and fog, the number of reports of riches and artifacts that were swallowed along with them steadily increases. Plus, with land slowly becoming a precious resource, treasure hunting presents itself as a viable employment opportunity for those who wish to set up a home in one of those ship colonies.
It's also a flame for the proverbial moths that others might just call nutjobs. If they had been talented combatants, they'd already be making fortunes as mercenaries and assassins for the petty and corrupt citizens who actually have resources to spare. If they were smart, they'd be searching for cures alongside a well-known but woefully misunderstood group of scientists and brainiacs who call themselves The Symposium. Hell, if they had any common sense at all, they'd just try to make a living on solid land like humans are supposed to do.
Instead, you found yourself part of a crew, and one that doesn't even pretend to keep up the pretenses of only being in the business until they find a place to settle down. No, you're in it for the adventure as much as you're in it for the money. Very few people survive being close to the black tide while retaining sanity enough to tell about it. You want to get filthy rich and maybe, just maybe, you're curious about all that impending doom crap that the crazy-eyed bartender told you about before he cut you off for never paying your tab. Maybe you're a little more heroic than that and you want to confront the beasts of the deep to make the Scrapsea a safer place for those around you.
No matter your motivation, you've found yourself on a ship with quite the ragtag crew, and you're about to embark on a journey that takes you far from anything you've ever known.
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Besides fantasy, which this RP obviously fits, I'm also listing it as Steampunk, because I figure that's where the level of technology will end up. There will be some sorts of tech scattered around the worlds, but it won't function quite like you'd expect, hence classing it all under steampunk best I can. One big influence, in terms of magic and technology for this game, is One Piece and a few other anime, but don't worry if anime isn't your cup of tea. Borderlands, Sunless Sea, and many other RPGs and games have also been an influence. Be as realistic or animu as you want, really. The world is quite ridiculous at its core, borrowing both from absurd, dark humor and also deeply serious plots as the story goes along.