This is the Pit of 100 Trials in Paper Mario: The Thousand-Year Door found in Rogueport Sewers. Enemies are easy to beat in early levels but get very hard later on. Every 10 floors there will be an item (Usually a Badge), a pipe to the entrance, a block that spawns the pipe to go down and sometimes Charlieton who has very high prices for items that could make you survive. Sometimes you may encounter a mover who can make you skip and go down floors for coins. At the entrance, there is a board saying the lowest floor reaches, a total of Star Pieces found and record Power Bounces. It is located near the Thousand-Year Door, and at the bottom awaits Bonetail, the oldest of the "Tail family" who was the Shadow Queen's pet, and she is stronger than her (the strongest boss in the game). Once you enter you can't save and you can only go up on every tenth floor or by the mover.
In the Nintendo Switch remake, after you defeat Bonetail, Whacka will move in and take her place as the final boss of the Pit of 100 Trials.
As Mario and his company advance down floor by floor, every floor will always have the same base enemy, but when they go into battle, the combination of enemies for the floor can vary. There are only three, or occasionally four or five, possible combinations though (With the exception of the 100th floor, in which case the enemy is always the same). Below is the list of all the possible combinations of enemies that can be encountered on each floor.
Electrifies Mario, causing most enemies to take 1 damage when they physically attack him. It makes Mario damage proof when jumping on electrified enemies. Makes some enemies unable to damage Mario whatsoever. Requires 3 BP.
A shiny Whacka Bump that cannot be eaten. Only available in the Nintendo Switch remake.
100
Area Tattles[]
This is the Pit of 100 Trials. That pipe just seems to lead down forever... Still, the air seems kinda fresh here. I guess it's flowing down from above, huh?
This is the Pit of 100 Trials, but I don't see any enemies in this room. At least there's a pipe to take us back to the entrance if you wanna bail. Then again, we'd have to fight our way back down to this level again... Better think it through before we do anything hasty, know what I mean?
This is an intermediate floor in the Pit of 100 Trials. These appear every 10 floors. At least there's a pipe to take us back to the entrance if you wanna bail. Then again, we'd have to fight our way back down to this level again... Better think it through before we do anything hasty, know what I mean?
This is the Pit of 100 Trials. We just gotta keep on fighting and descending... But this endless repetition of rooms is starting to totally wear me out, y'know? I guess we gotta soldier on, though...
This is the Pit of 100 Trials. We've come pretty far, looks like. The air's getting super-dank... Who knows how deep it goes, but let's keep going as long as we can...
This is the lowest floor in the Pit of 100 Trials. A zombified dragon named Bonetail used to protect this room. Yuuuuuck. Mario, I bet you're the first person to make it this far! I totally knew you'd do it! Now let's get out of this creepy place and back to the world above, OK?
Trivia[]
It is possible to access the Pit of 100 Trials before completing Chapter 1 by getting the sideways (paper-thin) curse in Hooktail Castle and then coming to Pit of 100 Trials before going up to Hooktail or if one is skilled enough, you can jump the bars with the spring.
If one is even more skilled, it is possible but extremely difficult to beat the Pit of 100 trials before fighting Hooktail.