The rat clawed it's way up the Ancient One's robe and sat on his shoulder.
The Ancient One had to have him, the boy. That exquisite boy, the only one who could quinch the Ancient One's ancient hunger. Hunger for his youth, long lost, hunger for it's vitality, also long since gone. The Ancient One would find a way to have the dark haired boy with the rich, youthful blood.
The rat crawled over to the Ancient One's ear and sank it's tiny fangs into the lobe. The ear lobe fell off easily and the rat nibbled on it.
The Ancient One would have him, if he had to sell his very soul, or what was left of it. Have him in every way that so repulsed the boy. He would wrap his rotten arms around the boys waist, laugh in his face as he tried to push the Ancient One away. He'd sink his moldy fangs into the boy's arteries and drink from his heart's fountain. He'd snuggle up to the boy's cries and despairation, cuddle to it and stroke it. This would be fun.
The Ancient One reached up and took the rat which had nibbled on his ear, and slowly crushed it in his palm. The rat screamed, it's arteries exploded, and a wet, dripping ooze slide over the Ancient One's hand.
Yes, this would be fun.