Sombritis

One dark night in Ponyville and the rest of Equestria, a dark, purple poisonous cloud swept over every town and city. This cloud was created by the most evil being in all of Equestria, the monstrous King Sombra. Known as Sombritis, what it could do was soon to be found.

Twilight Sparkle was the first to be infected. The disease soon spread, as it was airborne, and anyone who touched another would also be infected.

"RAARRGHHH!!!!", Twilight roared viciously as the strain infected her. Growling in pain, her bones cracked and shifted into an entirely new, monstrous form. Her wings stretched out so much that her bones began to crunch out of her body. When the transformation was complete, Twilight went on an unstoppable, bloodthirsty rage.

Twilight first found Applejack. She roared at her, catching the surprise of the cowgirl mare.

"Twil... WHAT IN TARNATION HAPPENED TO YOU?!", cried the orange earth pony in horror. However, she was not able to answer as Twilight leapt on top of her and began to eat her flesh. Twilight was no longer her normal self. She was a monster that could not be contained. Twilight used her sharp fangs to tear out Applejack's heart, and then tore out her intestines the same way. When she was finished with her feast, Applejack was left torn completely apart, dead as dinner.