Bippo Ernesti | Mystic Ark - Endless Stairs Bug @BippoErnesti | Uploaded 1 year ago | Updated December 09 2022
Bumped into this by complete accident the other day. Haven't found practical uses for it though. I spent a long time experimenting with the bug in various locations, but it's still likely I missed things.

As is stated in the video, it only works on west ascending staircases. East ascending staircases, downward staircases are impossible due to different trigger positioning.

"True" downward staircases are surprisingly rare, as after a while, most downward staircases start using a generic screen fade instead. To elaborate, note the difference in transitions on the downward staircase at 0:45 and the downward staircase at 1:15. The 0:45 variant is the rare one.

Feel free to stop reading now. The rest is part speculation, part experimentation.

*The Push*
The way the game deals with handrail pushing is slightly different, causing a very minor collision misalignment. This is what allows your character move a single pixel deeper into the north handrail than you normally could.

*The Sidesteps*
It takes one extra frame for the character to update their angle after receiving movement input, if you trigger the staircase sequence on the first frame, the game doesn't update the angle.

*The Combo*
Combining these two small oddities, you miss the trigger by a hair's breadth. Missing the trigger requires you to be misaligned by 18 pixels. Facing north while going up the stairs is 17 pixels' worth of misalignment, and the push provides the final necessary pixel.

*Limitations*
Why can't you do this with other staircases? Well, you would need two additional pixels of misalignment to miss the east trigger. This, however, is impossible, as two more pixels of misalignment would move you too far from the staircase to activate the sequence. Hypothetically, if you were to gain these two pixels *during* the stair sequence, you would miss the east trigger. Downward staircases require 5px extra for west descending, 4px extra for east descending -- also very impossible. There are some unique staircases on the Goddess' island which would require horizontal misalignment.

All the pixel stuff comes from crude hex manipulation. I also spent way too much time doing this.

Battles will not trigger, even if you were to move right over one. In certain (largely impossible) instances, you might regain control of your character, but you will only be able to walk in a very small rectangular radius, unable to do anything else.

Chapters
0:00 Explanation
0:24 Second example
0:41 Third example
0:58 Fourth example