I think it's unlikely to be possible but if it can somehow be done to get to the top part of Asylum Gateway early (without the Marcher Gad (walk on coals)) the any%/TAS route could drastically change and several minutes can be saved.

The top part has 5 quick dark souls for grabs. This means that all 12 Gateway dark souls can be gotten immediately + 3 Marrow Gates = 15. This means the entire Wasteland level could be skipped!

There are a few possible places I have tried and failed.

1. Pipe section with moving platforms. The walkway above it is just out of reach. There is a pipe high up you can just barely not reach the top of. If you somehow can, that's it.

2. Closed door close to Engineer Key. This door can only be opened from the other side with the Engineer Key. There is some small room on the sides of the door frame. I have tried to glitch through but failed. Perhaps and enemy can help but it's tough.

3. Boxes with dark soul on top. There are some boxes with a dark soul on top. There is some small room on the side of them. If you can get on top that's it.

Very unlikely it can be done but would be an amazing sequence break that saves a lot of time.

I have been trying quite a lot on N64 but I just can't seem to do it.

However, on PS1 it's a piece of cake! That version is awesome because you can easily lava roll over any coals. In Gateway just take the right route and lava roll across. Surprisingly easy to do. You just have to hold the crouch button as the roll is going on to avoid any damage.

However, a new hurdle popped up on PS1. You can't get on top of the Engine in Engine block! The bloodshot enemy just will not follow you to the engine room. He'll get to the first door and turn around every time. He can't walk through a closed door (like on N64) either. The room with the Engine is build quite differently as well. If anything, the engine is closer so the jump is easier to make. A normal jump at full speed just barely doesn't reach. If it is somehow possible to make it on PS1 that version would be easily the fastest by several minutes. I'm quite convinced the most important trick of all is impossible.

PS1 version would be easily the fastest for the 95 souls route. With the lava roll you can do many crazy routes through the game with less backtracking. It's pity because the entire 15 souls route is so easy on PS1 you can get to Engine Block every time in a single segment speedrun just not to the boss.

@WMJ Solved.

That looked surprisingly easy! Might give this one a shot now for a single segment run later.