(Yes, I know, it doesn't rhyme at all, and the stanzas don't flow all that well. Go ahead, shoot me.
I got the idea for this one right before I fell asleep last night... I'm kinda surprised by the "strangeness" of it, myself. 
It was just begging me to write it, so I did. 
Anyway, here it is.)
Lips like the ardent fire of roses,
Eyes like sapphires gleaming bright,
Teeth like creamy rows of pearls.
There she lies on her red velvet couch,
Reclining on her soft red cushions,
A picture alluring and yet so strange.
Dark hair spills over the edge,
Cascading waves of dark entrancement;
Her white hands repose on her ivory neck
As her head turns toward the open door.
A slender arm rises, sheathed in red,
Beckoning in the unknown guest.
Quiet footsteps enter the chamber;
Now she gazes upon the stranger.
But strange he is not to her,
Nor is he foreign, nay;
A form of smile flits over her face,
Her eyes, flashing, hold him captive.
Now then this strange lady and her guest
Converse in a tone hardly banal,
She promises him many things
If he will only let her lead him.
The man agrees - How can he refuse?
The lady's smile broadens:
But then a terrible, sudden change
Has begun to come over her features.
The man steps back, but the door slams shut:
No way out is there now.
As she writhes, the lady's laughter rings out.
"Trapped you are, never shall you leave!"
She taunts him, growing tall and dreadful.
Her form, her features, disappearing:
She turns into a hideous wraith.
"Fooled you were by my appearance,
Now for eternity your mistake you shall grieve.
Nevermore shall you know peace - for peace is unknown to me."
And then she looms up, fearsome, before him,
His fate seems sealed, his doom seems nigh.
But lo! There may yet be hope for him still.
It sort of reminds me of the part in The Silver Chair when the Queen of the Underworld changes into a serpent. Not really the same, but still. It kind of has the same feel.