There are quit a few patterns you can use to make a Cthulhu Ski Mask. I made my own crochet pattern.

It is an easy pattern and is made with acrylic yarn and hook 4.0 mm.

You need 100 - 150 gr yarn or 3 skeins of 50 gr.

The written pattern befits size large (head = 56-58 cm).

For a smaller size crochet a round less, till B, while increasing and make the eye sockets and mouth a bit smaller.
For a larger ski mask measure the head and increase some stitches more in the last increase round or make an extra increasing round.
For a good fitting mask take some measurements of the head and compare this with your work.