Pit of 100 Trials (Paper Mario: The Thousand-Year Door)

The Pit of 100 Trials of Rogueport appears in Paper Mario: The Thousand-Year Door. It is the first Pit of 100 Trials to appear in a Mario game, with Super Paper Mario expanding on the concept by introducing two new Pits: The Flipside Pit of 100 Trials and the much more difficult Flopside Pit of 100 Trials.

The pipe that leads down to the Rogueport Pit of 100 Trials is found near the entrance to the Palace of Shadow, which makes sense as, according to Grifty, the Shadow Queen created this dungeon and filled it with powerful monsters. She threw people she didn't like into the pit and left them to the mercy of the monsters down there. Sometime after her defeat the pit was closed off from the public.

The first few floors are considerably easy to clear, but as Mario progresses deeper into the pit the enemies become quite challenging. This is partially due to fact that Mario and his company get worn out by the relentless waves of enemies, but the adversaries themselves get stronger, culminating with the Shadow Queen's eldest pet dragon, Bonetail, inhabiting the final floor.

Every tenth floor contains a brief rest from battles, a treasure chest, and a pipe to take Mario back to the surface should he choose to use it, but no Save Blocks or Heart Blocks can be found anywhere in the pit. Accordingly, Mario is recommended to carry many healing items for his trek, and should master guarding and superguarding techniques. Occasionally, Charlieton or a Mover can be found; Charlieton offers to sell Mario items for an unreasonably high price (though they can spell the difference between victory or grueling defeat), while Movers accept payment for taking Mario back up to the surface or skipping him down two or five levels.

Two troubles at the Trouble Center require Mario to enter the Pit; Pine T. Jr.'s father needs rescuing on Level 18, and another trouble necessitates the destruction of a wall on Level 50.

Enemies in the Pit of 100 Trials
Each floor has one enemy in the overworld, but when Mario enters battle, there are usually at least 3 enemies in the battle, with the deeper floors having more. There is no way to get down to the next floor without winning the battle, as the defeat of the enemies causes a Pipe to appear out of the ground, leading to the next room of the pit.

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 clear the Pit of 100 Trials with only 5 HP, using minimum recovery items and without dying, by using the Danger Mario setup. This is when players use Chet Rippo to alter their stats, increasing their Badge Points and lowering their HP to 5. This puts Mario in permanent danger mode, and if the players buy and equip around 30 Power Rush badges from the Pianta Parlor, they can deal over 60 damage in battle. If player equips the badges, Spike Shield (allows them to jump on spiked enemies), and Ice Power (allows them to jump of fiery enemies), and then Multibounce, they can finish every battle in the Pit of 100 Trials in one turn. They can also defeat Bonetail in one turn, using Power Bounce. It would also be wise to equip the Chill Out badge, so Mario will never succumb to a First Strike by an enemy and therefore cannot be damaged before battle.
 * It is possible to complete the Pit of 100 Trials before Chapter 1 by getting the sideways (paper-thin) curse in Hooktail's Castle and then coming to Pit of 100 Trials before going up to Hooktail. It will take longer to complete however since the player would not have as many badges or high attack power and they only have Goombella and Koops fighting with him.
 * Dark Atomic Boo was originally supposed to appear on floor 50. It had 100HP, and was possibly removed due to the fact that players would already be hurt badly by the time they got down there, and would not be prepared enough for the boss fight.
 * Bonetail originally had 300HP and 9 Attack power, and could be battled any time the player went down the pit.