An elemental water moon inhabited by aboleth.
Slow life draining (-10 XP per turn for non-natives).
Slow life draining (-10 XP per turn for non-natives).
A quick spin on the Lovecraftian name generator gets us Sshuggall, which sounds suitably alien. Once they learn about the endless water and the constant XP drain, our heroes won't want to go to Sshuggall. As players, they'll actively resist it. The fun, of course, will be putting all sorts of plot hooks and powerful items deep below the waves. But I digress...
If you are very lucky, you'll find a guide to Sshuggal. And I don't mean luck as in good fortune - you're better off slitting your own wrists. I mean luck as in, "You've spoken with a mind flayer and struck a deal, and you've got one of the rare mind flayers whose crystal ship isn't just a deathtrap/slave-barge, and he'll actually take you to Sshuggal and possibly back again, without eating your brain." That's lucky.
If you want to push your luck further, you'll need equipment:
Bathyspheres. They can survive the crushing depths better than anything else. The problem, of course, is that they only go down. You'll want a teleport scroll for getting back up. Either that, or you'll need to pioneer some new technology.
A lead-lined ship. Supposedly aboleth have trouble seeing through lead. Good luck getting it to float!
Manta Cloaks. You know about these, right? Leather cloaks, you put them on, they create a magic globe of fresh air around your head? They're scarce but if you've got the gold, they're an option. They won't protect you from anything but drowning, though, and on Sshuggall that's the best way to die. You might find an old one from the Sahaugin Wars if you check the markets at Azerat, but there are so many military historians that the price is going to be sky high if it's in anything like good condition.
A map. It sounds juvenile to suggest, but it'll be nigh impossible to find a useful one. Nothing stays in one place for long on Sshuggall. A group of dwarfs went there a century ago - The Blackfrost Expedition. I'm sure you know this story. Two hundred dwarfs in full battle regalia with rune-wards and enchanted hammers, state-of-the-art diving spheres, the wealth of an entire kingdom spent on plundering the grim halls of the aboleth? One lone survivor, completely insane. They found incredible wealth but they couldn't escape with it. The walls had shifted. Their ships were on the other side of the iceberg. There was no way out. They needed a map that could change when Sshuggal changed. It's always changing.
Where You Think You're Going (Roll d8)
1. Iceberg
2. Black Stone Pyramid on an iceberg
3. Stone Tower (half-submerged)
4. Stone Tower (fully submerged)
5. Giant Bubble with impossibly stable shimmering walls
6. Aboleth City (ocean floor)
7. Fossilized remains of a gargantuan Angler Fish (ocean floor)
8. Glacial Chasm
Where Are We Really? (Roll d8)
1. Inside the dream of a twenty-thousand foot tall slumbering stone colossus. It dreams of being alive, for the very first time, and of all the wonders it will wreak.
2. Shrunk to the size of cells, tracing an impossible course across the mucous membrane of the nostril of the party's fighter.
3. We never left the ship!
4. In a pyramid inside a pyramid inside a pyramid. The pyramid is the key to everything. If we can just get to the true pyramid, we'll find our answers. Everything is going to be okay. Everything is going to be okay. Everything is going to be okay. Everything is going to be okay.
5. Exactly where you thought you were.
6. The belly of a moray eel, the incredible size of which means it cannot possibly be a moray eel.
7. Floating blissfully through a bubble of liquid euphoria. You've heard that the aboleth use these as defense mechanisms, but you don't care.
8. Inside a temple filled with idols to ape gods, fire, and warm-blooded things. There are humans here, though they hide their appearance beneath black robes, and while they might share a fascinating history of how they came to live on Sshuggall, they have knives and oh god their eyes, what's wrong with their eyes?!
I could go on. I probably will, at some point. Sshuggal is the death-trap that won't let you escape until you're good and level-drained. It's going to require a good deal of prep so that it's not purely arbitrary, but it's a great spot to throw in random generators and non-intuitive puzzles.
The aboleth went extinct here centuries ago. That doesn't mean they don't still show up - time isn't linear on Sshuggall, after all. It just means Sshuggall has far worse dangers than even the aboleth could withstand.