Here is the full list of all 21 Pesadelo - there are Regressão achievements.
You burned the 4 treasures
"listening to a radio" you heard all radiologs
You get all documents
First entrance in the Eucaliptal
Burning all 4 poisonous flowers
Make the Orchid Soul poison
Makes 5 Arnica's Drink
First entrance in the Cave
Found the code, you know multiply!
You like papers. Pick up 10 documents
This is just the beginning. Died 5 times
This Archievement is not for you. Thanks Oblivion.
First entrance in Black Oak Cemitery
Found the mausoleum key
You found all the literature of Cordel
You play the Melody of The Pain
You won the cursed priest
Break all the chalks and pens
You found the secret door of the church!
You finished the Pesadelo – Regressão