Here is the full list of all 21 Occult achievements.
mirror quest finished
big bang
kill mediums
killed the Spiderlady
open 3 locked doors
open lockers and drawers 50 times
25 window jumps
found the phone and answered the call
throw a friend out of the cupboard 5 times
helped a friend get up
sat in the closet for more than a minute
first time stunned by a monster
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 with train
defeat the evil