Extra NaPoWriMo: Nightmare

When I sleep I am a nightmare.
Stars don't know what to do.
The moon frowns so hard
it tilts over.  I swarm across
the planet with my mouth
wide open, each individual
fang with a dreamer in mind.
They try to ask the tree
outside the window to eat me.
They beg for witches to cast
a spell on my horrid head.
They'll admit to every failure,
every sin, if I'll fly away.
Except I have to feed
the snakes in my hair,
let them torture my victims
with each strike of poison.
Is there a text they can read
in my face, a few words
that can turn me back?
It would matter if they
owned the Bible, recited
each chapter and verse.  If
they wrote a hundred more
prayers, if they were chosen
as saints.  I have a black
tongue that closes their eyes,
that licks their foreheads,
that leaves a last symbol
when they wake, visible
only to them.  It means
I'm theirs, that each night
it glows, each time I taste.