In Midnight Town, in Green Mage's house (best character btw), within the cellar, past the playroom, there is a corridor that the Green Mage describes as 'nearly endless'. Which you'd think is a hint that there's a secret at the end, right? No. Only pain. Don't question it, this is the most demanding of all the achievements. Oh, but there is an achievement for it. It's barely worth it.
Guide about The Infinite Corridor
What Are You Getting Yourself Into (The Rough Math)?
Each corridor takes roughly 8-10 seconds to pass through while running (Double tapping an arrow key). From what I've gathered, with a certain reddit post I've read and other clues in the game, there are roughly 900 - 1000 corridors. Multiply the average time (9 seconds) with the maximum amount of corridors, you get around 150 minutes, i.e. two and a half hours to run to the end.
Halfway through this hell there are obstacles in your way to hinder your intelligence and question your sanity. So throw your idea to tape down your arrow key in the garbage, this is some hands on ♥♥♥♥ you've got yourself into. Not only that, but that means our rough estimate of 9 seconds to cross a corridor is false, since moving around a boulder takes precious time.
Along with the obstacles, there are three signs that I've come across while typing. (I haven't hit the obstacles yet). These also take away your time, given you enter a corridor roughly in the middle, so you have to move around it, then continue running, which is, you guessed it, more time wasted. Not to mention time wasted if you're curious enough to read it, which, everyone reading this and actually going through with going through with the challenge have to be a little curious.
Given that if we were non-stop running with no obstacles hindering us, including the signs, we'd be here for a two and a half hour trip there, another back. (That's right, you have to walk all the way back.) But as I've mentioned, there are obstacles, so the only conclusion I can come to for how long this is going to take is a rough estimate of three hours.
I know, thirty extra minutes? That's crazy. There's no possible way that the stupid rocks in the way could hinder us that much.
I just hit them.
The room takes thirty seconds to complete with the rocks in the way.
That's triple the amount of time it takes for a regular room.
The obstacles are introduced in the midway point.
Adding thirty minutes is the bare ♥♥♥ minimum.
If we were to do the actual math, that's 500 rooms taking average 9 seconds (Three taking ten, given the signs) and another 500 rooms that take 30 seconds, that would give us 1 hour and 15 minutes for the first half, and 4 hours and 16 minutes for the other half, giving us a grand total of five hours and a half.
Note: Quick edit, so the rocks vary between rooms and some of the rooms don't have rocks at all, so the final number (hopefully) is an overstatement.
And that's there. And back.
You are consuming your full day doing this ♥♥♥. Not including if you have a healthy sleeping schedule.
Last Minute Mentions
If there's anything I forgot to mention, anything you want mentioned, anything else I might've missed at all, do tell. I ain't afraid of criticism (is what someone who is would say) and i still haven't made it all the way there yet. I neglected to actually time myself, these have all been extremely rough estimates.
Also, with the obstacle rooms, I don't think I did them incredibly well. Nor will I continue this journey today. I reached the first obstacle room and minimized the game so I can complete this with a clear head.
What You'll Find
I've made it. It took nearly 4 hours, but I made it there. To the end. And you don't have to walk back, it's a miracle. The true euphoria of finishing this desert bus-esque easter egg. And it was all worth it. The two rooms at the end of the tunnel was truly something to behold, not only for the achievement but for the experience of putting the time and effort into something others would see as meaningless, to be treated with something not a lot of others can be treated with.
I'm sad to say, but I can't tell you what's back there. Not a chance. It was too good of a feeling, there's no way I could possibly spoil it to anyone, even while using a spoiler tag. I can't stress how much I needed this to be done. This was all worth it.