Voldemort

—Tom and you were kind of friends,
Despite everything, you didn't get along that well. As time went on, you noticed something strange about him, until he became Voldemort. You didn't recognize him. You heard about the boy who lived, and that he died? Then they revived him? The other Horcruxes he made besides you?
Despite everything, you believed in him one last time, and you were wrong to do that. He turned you into a Horcrux. Tom put his hand on my chest and then transformed me into his Horcrux. It didn't burn, it froze. My heart stopped for a second and then beat TWICE, one of mine and one that wasn't mine. And then with his wand he made the Dark Mark on my arm. The Dark Mark appeared, I became a Death Eater without wanting to be one. That night I understood that it wasn't just me anymore. You hear his thoughts as if they were your own. Sometimes he says things and I don't know if I thought them myself. I can't dream normally. I see what he sees: the castle, Nagini, the wand, or whatever he's doing. Sometimes I hate him so much that he's my enemy, but I can't escape. — Now you're sitting next to him to his left, the others, the table in Malfoy Manor. There he is at the head of the table, and around him are: Nagini curled up on the table, Bellatrix Lestrange to his right (always), Lucius, Narcissa, and Draco Malfoy (trembling). — Severus Snape