Start out with an eye.
Contort it.
Make it red.
Have it drip.
Out of the drips form hands
Clawing their way out.
Make it shout about the ugly insides.
Turn the hair to spiders
That crawl on the face,
Then disappear through the holes
In the skin
That begins to melt from the bone.
Turning this Thing into a skull
Wrapped up in vines
That turn black and smolder to the ground.
Zip up the lips
With a scarred twist.
Stitch it up and call it a day.
I think this illusion looks monstrous enough.