The monster under the bed

Sliding through that eternal door,
I can't bear to watch the blood and gore,
The creature struggles out of it's shell,
Of this monster no one shall tell,
The creature turns its massive head,
It might be sitting under your bed,
Sliding, sliding forever in the dark,
Then you hear the car park,
The feet running up the steps,
The door slowly opens, you can't believe what you saw,
Your parents see you in the gaping jaw.
This monster likes its humans raw.