Watery Labyrinth Area in Shadow Tower would make Blighttown, Valley of Defilement, and The Gutter all rolled into one seem like a pleasure resort. The "watery" labyrinth is flooded not with poison but with ACID, which eats away at the durability of everything you have equipped, as well as at your health. And rather than being a mostly inconsequential mechanic, as in Souls, item durability is at the forefront of the game - everything has low durability (a weapon with over 20 max durability is likely to be an end-game greatsword) and degrades fast (each connecting weapon swing removes at least one point). Also, for every point lost, the item's properties are also reduced.
The only way to restore durability (other than using a limited quantity rare and expensive consumable, which only restores a few points of durability anyway) is to find a demon merchant who repairs any item to full using your life essence - i.e. he takes away your Hit-Points - with most decent items requiring nearly all of your HP to restore. And the only way to restore HP is through health potions, which are somewhat rare (though all of them restore your HP to full) or by having the demon merchant convert pieces of gear into health (and thus reducing the pool of spare gear you can use when your main stuff is close to breaking). So, even without trudging through a maze full of acid, there's a constant balancing act between durability, hit-points, available gear, and consumables.
Of course, none of these merchants are anywhere to be found in the Watery Labyrinth. And, as Shadow Tower is an RPG rather than a twitch-fest, taking off your armour to avoid it being eaten away by acid will vastly reduce your effectiveness, taking away health, defense stats, and even offense stats. Plus, you still have your weapons to worry about; you can't rely on magic attacks because in ST magic is cast from magic rings, taking away 1 point of durability for each attack, and with most rings having about 10 durability each. They will also face further corrosion as you stand in acid.
I don't think I need bother mention that the enemies fought in the area are some of the toughest hitherto faced. Including hordes of serpent-men who emerge from the acid in ambush and gangbang you with claws, unless you spot the tiny bit of rock in the distance that's sticking just out of reach of the acid's effect and walk slowly (yes, the acid of course reduces movement speed also) towards it so you can fight them on safer ground - at which point they'll just laugh and spit their own very deadly poison AoE onto the rock, forcing you to dive right back into the acid...
Fromsoft sadism at its finest.
