This walkthrough comes straight from steam wich you can find here.https://steamcommunity.com/sharedfiles/filedetails/?id=19665...
Credits to Omega Ridley
Unlock every Trickster Door.
Notes: There’s a total of 12 Trickster Doors in the game that are required for this achievement. 11 of them are found in the main story Chapters, one per Chapter, and a secret twelfth door can be found in the Void. You’ll need to find and use every single Trickster Key found in the main game, which means you’ll have to go through levels again to find all of them and use them on the doors themselves (note that if my instructions are not enough, you can always check your map ! The doors are marked with a special icon).
I will not be showing the location of every key in this guide. Don’t forget you can also buy a couple of keys from Vulgrim himself in the Void. Without further ado, here are the locations of the trickster doors in every chapter as well as the hidden one in the Void:
Chapter 1, Dethroned: The door is located at the very end of the level, AFTER your meeting with Samael. You’ll find yourself inside the Void. The Door is slightly off the beaten path, just keep moving right instead of entering the circular room which leads to the Vorpal Blade, and the door will be waiting for you a little further ahead.
Chapter 2, The Slag Pit: The door is found right at the beginning of the level, in the very first room you appear in. Just head towards the northern wall, you can’t miss it.
Chapter 3, Inferno Vault: Right before the entrance to the Vault itself, you’ll have to activate two switches to open the gate to the dungeon. From the entrance itself, go northwest until you find a snowy path and keep following it to find the door.
Chapter 4, Icebind Cavern: Follow the steps to reach the Void Rift at the top of the cliff, which you can find in the “Close the Rift” section of this guide. Instead of dealing with the rift however, continue your path towards the northwest past some crates. The door is located at the end of the path and can’t be missed.
Chapter 5, The Hoard: You’ll have to enter the fortress through the main gate and defeat the Legion Boltsplitter blocking your path. From there, head north, to the left of the elevator platform that became available after beating the miniboss. The door is found towards the end of the path, to the northwest.
Chapter 7, Decay: The door is found near the beginning of the level. As you enter the large swamp area, head east until you reach the area called the Mire. There, jump on top of the rocky formation in the middle of the swamp, and head north along the wooden bridge. Follow the path until you reach the end, where the Trickster door is located.
Chapter 8, The Holdback: One of the trickiest doors in the game. It is found at the very end of the level. When you reach the part where you have to use War’s Vorpal Blade to raise a bridge from below the corrupted water, turn back and head south. You should see some broken stairs to your right. Follow them and jump down to the lower level. Head east until you find a Trickster door buried under a pile of rubble. Don’t worry, it’s not the real one !
To the right of the door, you’ll find a small path leading to a drain pipe. Jump into the pipe and fall down to the lower level again. You’ll know you’ve reached the right spot if you find yourself next to the final valve and a blue flight orb. From there, head northwest and you’ll find the door !
Chapter 11, Bastion’s Fall: This door is located near the beginning of the level. As you come across the first river, follow it north and go through the waterfall (I love that one of gaming’s oldest tropes keeps getting used to this day). Defeat the enemies in your way and you’ll find the trickster door waiting for you.
Chapter 12, The Maelstrom: Head as far east as possible, until your reach the edge of the level. From there, head northeast and you’ll find the door.
Chapter 14, The Dredge Works: As you reach the giant barricade, you’ll find a path on the leftmost tower that allows you to climb to the top of the barricade and head southwest until you reach a small ledge leading back down to a horse-blocking seal. Pass the seal and follow the desert path southwest, the door will be waiting for you at the end.
Chapter 15, War Machine: The trickster door in this level is located near the end of the level. At some point, you’ll get ambushed by waves of enemies as War and Strife talk about drowning Moloch in a river of blood, that sort of thing, before a bridge drops down. At this point, backtrack to the northeast instead of progressing, and you’ll spot a couple of pillars you can climb up and down. Drop down to the lower level, and you’ll find the trickster door to the northeast.
The Void, Secret Trickster Door : The secret final trickster door is found by completing a series of puzzles and platforming challenges in the Void. You’ll need to have all the upgrades to make it through this section. From the central platform where you select the level you want to play, go east and jump onto the small floating formations until you reach the blue orb.
Use it to fly up and reach the platform to the right. Here, use War’s Vorpal blade to transfer the flames to the torches you can spot on the other side of the wall by making the blade bounce off the wall.
From here, a series of puzzles await you, making you use all your abilities, including the Tremor Gauntlet, Void Bombs and even the Aether Spark in one of the most difficult challenges the game offers. After you succeed, you’ll be greeted by the final Trickster door, which requires a whopping six keys to open. Once you open it, the achievement will unlock.
Here is a video to show how the puzzle in the void goes. And the Trickster Boss fight is included in the video.Credits goes to Bigdaddyjende
for making this video