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