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