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