(Authors Note: PLEASE READ* Derpy isn't going to act like expected in this story. This story was actually a product of a question a friends asked. She asked me "Is Derpy naturally like she is, is it a blonde thing or is she hiding something?" So this story gives a possibility of what if she is hiding something...)
1450 years ago......
The sound of heavy footsteps followed the grey mare down the dark ally as she ran, a bundle covered in a shroud in her hooves.
"No! Stay away! Leave me alone demon!" She continued to run, the silhouette of a taller alicorn silently stalked her before ducking into the shadows. She continued to run until a tall, faceless mare grabbed hold of her as the alicorn approached.
"Domine, Pater coeli et clypeo protege me a malo ..." The mare cried out as she scrambled for the rosary in her pocket.
"...in lucem sanctam dilectionem." He laughed, his fangs glinting in the moon light as he caressed the cheek of his prey. " Putasne vere, soror Annabel, ut eruat vos Dominus Deus vester?" He licked the tear off her cheek and sniffed at her neck gently.
"Don't you touch me, you demon. Agent of hell! Return to the lake of fire from which you came!" She spat in his face, his anger rising, but loving the fight his prey put up.
"Oh poor Sister Annabel, why won't you just give in. You know your going to love it." He cooed with a sinister grin as he pulled the rosary from her hooves and crushed it. "No be a good little mare and give in." Before she had any time to react, his fangs were sunk deep into her neck. Annabel let out a loud scream as the blood began to drain from her body. The pain was excruciating, but only lasted a moment before her body went limp and fell to the ground.
The alicorn licked his lips, gathering the last bits of blood that had been wasted on his muzzle. "Mmm... the taste of damning the soul of the clergy. It's simply divine." He gave a horrid laugh as he ripped Annabel's barely beating heart out and crushed it wiith his magic. "Come, Slendermane. We have much more to do tonight." They started to walk away when a small cry came from the dead nun's hooves.
"Hmm." He walked over and moved the shroud from over her body, his eyes lighting up with savage horror and a fiendish grin passed over his face. Under the shroud laid a crying baby pegasus, her grey body and blonde mane matted and messy from the heat within the shroud."Well what do we have here."
Slendermane walked up to the filly, extending one of her long tentacles before having it smacked away. "No,you may not have her. I have a plan for this one." the alicorn slit the end of his hoof with his fang, dripping the blood into the filly's mouth and on her forehead as he began to chant.
"Damnatorum Domine, tibi sacrificium pro puero isto sanguine Genetricis Pater aeternus. Damnatorum Domine, tibi sacrificium pro puero isto sanguine Genetricis Pater aeternus.Damnatorum Domine, tibi sacrificium pro puero isto sanguine Genetricis Pater aeternus!" As he chanted the filly's body began to tense up and she began to scream. Her eyes began turning red and fangs sprouted from her gums.
The alicorn laughed as he walked away, Slender Mane walking close behind him. "Remember my name young one, for one day you shall praise it. Remember it well....."
Present Day
"Dragonimar!" Derpy shot up in her bed panting like crazy. "Dammit not again." She held her hoof to her head, wiping the sweat off her face, her once yellow and odd looking eyes were glowing red and...still odd looking. Two large fangs hung down from her muzzle, but only a few knew about them.
She got out of the bed and stretched her wings out, her eyes changing back to there normal blonde color and her fangs retreating back into her gums. She sighed as she walked out the door, grabbing a muffin and beginning to go about her day job. Ponyville Mail Carrier and all around ditz.
The perfect cover.