Here are a few scary filter apps I hope youll enjoy :)
SNAPSEED
This, the best for scary effects.
In snapseed, scroll to the right until you find 'drama'
Hit the star
Hit 'dark 1'
Play around with this! If the filter strength is too much, just simply take your finger and slide your finger left to make it go down, right to lower it.
PICSART
Not the exact best for creepy, but, if you feel like your creepy image is too dark or too light, this is the app!
Open an image by pressing 'edit' then 'gallery' choose your image
Hit the 'tool' button
Hit 'curves'
Now, move your curves down to make it darker, up to make it lighter. Play around with it some :)
Thats it :) ask for more tutorials!