The Terrifying Creature in My Mind

The nightmare in my head
Wouldn't go away.
It was frightening and scary
And pounded my head all day.
A creature entered my shadow.
It was over eight feet tall.
It had a long, slimy tongue
And climbed up on my wall.
It's skin was green and leathery.
It's tail was curvy and thin.
And as I turned around,
The creature spoke from within.
"You mustn't worry about me.
I'm not going to harm you at all.
I'm just part of your imagination
That is here for your beckon call.
I may look rather repulsive,
But I assure you that I am not.
I do not plan to kill you.
Well, at least not on the spot."
I pinched myself several times
To get the creature out of my mind.
It finally left my head
After a big pinch on my behind.
I hope that I never face it again.
It could be my mortal doom.
Thank heaven the slimy creature
Decided to leave my room.