A nun's habit is a fairly straightforward Halloween costume idea, but it can be modified to add a spooky twist to this conservative look. Surprise your friends and fellow Halloween party guests or trick-or-treaters with a spooky, creepy Halloween nun look. Distinguish your costume from other costumed nuns with a few ideas designed to take your nun from normal to scary.
Paint your face to look super spooky. This could be just using white and black paints to create a skeleton look with black eyes and a black nose, or a zombie look using green, red and purple paints to look like an undead nun. Alternately, pull on a scary mask to change your costume's mood.
Dye the white parts of your costume a deep, gruesome red. Take the white collar and headpiece from your costume and follow the directions on a box of red fabric dye. Adding red to a nun costume will up the surprise and scare factor a bit.
Add some scary accessories. A classic knife in the chest, arrow through the head or fake gashes along the neck are all scary examples. Check out the costume shop for elements of creepiness that you can add on to your existing nun look.
Grab a prop. A hatchet, bloody knife, noose or other horrifying weapon will work. Dribble fake blood all over your nun costume, your skin and the weapon to look like you are a nun that has been on a bloody killing rampage.