When making creepy ilustration there are some resources that can become useful just to transmit the creepy feeling into the drawing, by adding the correct atmosphere, lighting and textures you can transform a plain sketch into a piece of art.
Step 1: Setting the scenario
1) We are going to open a new file and sketch a cemetery, you can just sketch some basic lines and maybe a character It is very important to set the position of the objects correctly to make a better drawing
2) Open The copic library and choose a dirty brown from it with the marker tool we are going to make lines to color the sky
3) Keep coloring the sky with a darker color untill you saturate the sky
4) If needed with a light gray put some highlights to make the sky look ghostly
5) Color the ground Black