Disclaimer: I own neither Twilight nor Harry Potter, just the jokes I was making when Cedric Diggory died.
Carlisle was indulging a favorite habit of his, wandering around graveyards in hopes of finding a new "friend", when he saw some lights off in the distance. Curious, he ran to the scene and beheld two boys popping into existence. They dropped a trophy between them. They said something, but Carlisle ignored them in favor of watching the strange neon green lights that started to appear in the air. He streaked behind a tombstone as more people appeared. Peeking out over the top of it, he flinched as more green lights buried themselves in a boy with brown hair. The other boy started screaming and crying, before his attention was distracted by something else. Carlisle ignored the boy and whatever was distracting him in favor of crawling over to the young man with the brown hair.
Carlisle put his head near the boy's chest and heard the didn't hear the sound of a heartbeat. To confirm it, he put his hand over the child's chest and felt no heartbeat. Carlisle knew he only had a few minutes to act if he wanted to save the boy, so he quickly picked up one limp hand and bit the crook of the elbow. Feeling a frighteningly evil gaze on him, Carlisle hid behind the tombstones again and resolved to follow the boys- if he could.
Carlisle was very confused when the battle, for that's what it seemed to be, was over. The boy he had injected with venom was being sobbed over by the other boy, who looked beat up and had apparently escaped from the evil he sensed by the appearance of ghosts. The strangest part however, was when the sobbing boy grabbed a large trophy and just disappeared. Carlisle blinked and ran away before the evil could turn it's focus on him. Being immortal and near invulnerable didn't mean he wanted to tangle with whatever that was. He knew the boy he had just turned would find him soon. After all, blood calls to blood.
:)