...where you enter a fog door to go into a small room with a spirally staircase going down. Fog doors are one-way until you beat the boss beyond 'em, so you are effectively trapped in this room. Since you have no other options, you go down, only to notice the stairway stops abruptly, and there's nothing but a pitch black abyss below you. Some helpful bloodstains might be around, telling you jump down, and be careful, so you drop down and die. Annoying, but you might assume you missed something, so you go back and give that room another thorough look, however doing that will get you stuck again. No way out other than to die in the abyss yet again. Looking up online, you find that you actually have to defeat a boss before you can go there, so you look for the boss, but somehow the game glitches and the boss doesn't actually reappear once you died once. Turns out the boss can jump out of bounds and kill itself.
Well, the boss is gone, so time to try that one one fog door in New Londo Ruins again. Unfortunately you still die when you drop down. Time to Google it yet again. Turns out you needed to fight Sif to get a ring. The ring makes a reference to "the abyss" in its description, but I wouldn't have known the New Londo Ruins door was leading towards that had I not looked it up. Questionable progression and flow aside, none of that was helpful since Sif's gone and lost access to its loot. Luckily the Sif glitch was common enough that plenty of folks had been asking the question already. Rather than fixing its shit, From added a bandaid solution where they dumped the ring in a chest near Frampt. Not sure how they expected people to know this, but whatever. At this point I was ready to get it over with So multiple detours later, you're finally back in that one spot in New Longo Ruins with your ring so you can drop into a nameless hole that you're supposed to smell that it's the Abyss. Definitely remember to equip the ring though, since magic rings don't work passively, and your character is really fussy about the amount of rings you can wear at the same time.
The whole process felt like some Castlevania 2 nonsense. I'd have no clue what to do half the time, and nothing about it guided me in the right direction. I had no context what or where the abyss was, or why it was special in the sense that it operated on different rules than the rest of the game. Experimenting myself even pushed me to the wrong conclusions. I think even if the game didn't glitch out on me with Sif, I'd still have to look it up.