Mt. Nibel Wrong Warp
The Mt. Nibel Wrong Warp is a version of the Wrong Warp glitch, which makes use of the Kalm flashback "no rewards" battle flag.
Execution
In order to perform the Mt. Nibel wrong warp, the player must first have a save file with its Game Moment value set to a value less than 385, which equates to before or during the Kalm flashback sequence. In this state, if the player enters Mt. Nibel, a battle flag is set that skips the battle rewards screen after winning a battle, sending the player directly to the field module. Since this battle flag was not intended to be used outside of the Kalm flashback, it behaves incorrectly on the world map, sending the player to erroneous locations—either to the field currently loaded in memory from a previous game over (Mt. Nibel), or if no field is loaded, to a location based on the ID of the last battle the player was in.
Use in runs
No setup save file (PC Any%, All Bosses (Warps))
The player must have a save file with the Highwind available, but with a GameMoment value less than 385. For NG+, this is a pre-prepared save file, but for All Bosses (Warps), it is created during the run. In this save file, Cloud will be standing next to the back entrance to Mt. Nibel, with the Highwind nearby.
Once the player is ready to warp (after first exiting Midgar in NG+, and just before the North Crater boss rush in All Bosses), the player must make a save on the world map, then restart the game. Then, to clear some memory that interferes with the warp, the player must reopen that same save file and immediately save over it. With this done, it is safe to restart the game again and load the warp setup save.
At this point, the player must run into Mt. Nibel. If GameMoment is less than 361, a short cutscene will play off-camera. The player must then immediately run back out to the world map, and take the Highwind over to Gold Saucer area. In this area, the player must find the encounter with the ID of 96 (3 Spencers and 1 Flapbeat). Once found, the player must kill their own party members to intentionally trigger a game over.
The player can then reload their main speedrun save, and, without entering any fields, win the next battle. If done correctly, the player will be warped to the south room of the debug room.