Castle of no Escape

You unlock this achievement by reaching the sixth floor with any character. You can do so in three ways. You can climb up stairs from the fifth floor. Interestingly, if you climb down stairs from the first floor (your starting floor), you will end up on the sixth floor. Additionally, you can warp to the sixth floor.

A warp is a glowing pinkish white orb. It will send you to a random location on the same or different floor. So, from your starting point, it is possible to reach any of the other floors. It is also possible for a chest to contain a warp that will send you to a random location on any floor including the one you're on.

Start a game. Choose a character: for champion, for wolfman, or for Shamaness. Since your objective is to find stairs or warps, move as quickly as possible from question mark to question mark. By moving quickly, you avoid most of the game ending adversities and can quickly identify stairs or warps that will take you to a different floor until you reach the sixth and unlock this achievement.

If you get a game over, you have lost very little time. There’s a lot of luck. Moving quickly avoids most of the bad luck. By the same token, your good luck might find a warp that takes you to the floor you want.

For first time players. It is possible to unlock any of the five DLC achievements as your second achievement in the game. You start the game by pressing after the loading screen. You select your character as stated above by pressing either , , or . Since there is an achievement for starting as each of these three characters, you will automatically get an achievement.

Move by pressing . The analog sticks do not move the character. When you move into a square with a question mark, its contents are revealed. A chest can be opened, flared (if you have a flare), or ignored. You can backtrack to squares whose contents you've revealed and you may have tactical reasons for doing so.

One tactic is to move into a square with a question mark and immediately back into the square you came from. That way, you can reveal the contents of the new square with little risk to yourself since adverse effect squares take a second to activate. If you get game over, you start over as a brand new game: you select your character and move on a randomly generated map.

TL;DR
You can do it in one minute:

The Staircases will loop so if you find one going down in Floor 1 you will immediately move to Floor 6 and so on.

Move around either going up and down the stairs until you reach the 6 floors.
Use flares (in case you have them) to reveal your surroundings in case you have trouble moving around.