Here is the full list of all 21 Occult achievements.
complete the game alone
caught 25 spiders
died from the fall
mirror quest finished
killed the Spiderlady
throw a friend out of the cupboard 5 times
collected 10 jewelry
found the phone and answered the call
open 3 locked doors
5 minutes to stand by the car
25 window jumps
sat in the closet for more than a minute
open lockers and drawers 50 times
helped a friend get up
first time stunned by a monster
start a game together
start a four-player game
kill mediums
big bang
kill with train
defeat the evil