Here is the full list of all 54 Withering Rooms achievements.
Strengthen your body with some help.
Enter the wrong room.
Obtain an oil lamp.
Craft your first item.
Kill something or someone.
Complete the Prologue.
Complete all arena challenges.
Win your first Arena battle.
Have at least 150 coins at once.
See the Blood Tower from a distance.
Defeat a foe in the basement.
Defeat a foe in the labyrinth.
Defeat a foe in the church.
Defeat a foe on the roof.
Defeat a foe in the entrance hall.
Defeat a foe in the hedge maze.
Defeat a foe in the valley.
Defeat the final foe.
Defeat a foe on the upper balcony.
Defeat a foe to the east of the house.
Defeat a foe in the baths.
Defeat many foes in the cemetery.
Reach the Byzantine Labyrinth.
Take a picture with 5 or more subjects in frame.
Capture a spirit with a camera.
Complete the first chapter.
Complete the second chapter.
Complete the third chapter.
Complete the fourth chapter.
Achieve ending A.
Achieve ending B.
Achieve ending C.
Receive your first firearm.
Tell Josette the truth.
Earn your Initiate Outfit.
Complete a plot against the king.
Reach level 40.
Kill 25 things in a single night.
Kill 50 things in a single night.
Obtain all 4 Night Mother's Instruments.
Reach Nowhere.
Rescue Felix and Horace.
Do everything the king asks.
Harden your body with ancient blood.
Harden your body with organ grease.
Enter a different wrong room.
Obtain all outfits.
Activate 5 Remembrance Shrines.
Find all bestiary pages.
Activate 20 Remembrance Shrines.
Defeat a foe in Central Nowhere.
Defeat a foe in the Cholera Clinic.
Defeat a foe in the Blackett House.
Achieve ending D.