Pride
"You're going to starve."
Voldemort opened his eyes and stared across his cell through the small, square glass panel where he could see the face of his greatest enemy; Harry Potter. It was odd. The boy was the only one who had ever shown him an inch of kindness, all else had dismissed him as a crazed little boy, evil wizard, megalomaniacal Dark Lord. Yet, it was the same boy who had forced him to surrender to prevent his own death, the same boy who demanded mercy for him. He had killed the boy's parents, was the cause of many other deaths of those close to him. Here he was, trying to get him to eat.
"I will not eat the shit they call food." Voldemort spat. Even back at the orphanage, decades ago, he was served more edible food. Stale bread, watery oatmeal, and, occasionally, a half of a dry apple easily beat the bowl of brown chunks he was given for every meal. It looked like it came out of the behind of a House Elf. It probably did.
"If I get you better food, will you eat?" Potter asked.
"Yes." Voldemort said, laying his head back on the stone wall. "Why do you care?"
The boy stared at him. "Eat what they give you." He ordered, then walked away. His shoes sounded against the wall outside, tapping its way into the cell, muffled but there.
Three hours later, Voldemort was served a steak cooked blue rare, a baked potato, steamed green beans, and a goblet of pumpkin juice. He enjoyed every bite and left the tray empty, back in the tiny slot at the bottom of the cell door.
Voldemort didn't lose track of time, kept track of the dates with ease inside of his head. He went over magical theories and history, every choice he's made since he was three years old and he chose the brown shoes over the black because they fit better at the time. His fingers would twitch and he had to remind himself of patience, if he escaped Potter wouldn't hesitate to end his life and destroy the last piece that ensured Voldemort's immortality. He could rest in a cell for as long as he needed, as long as he lived.
Potter visited him often. There were weeks with daily visitations. The boy asked questions that often got no answer, but he mostly sat by the glass panel and read books into the small holes through it. He talked about politics and worldly happenings. He talked about his loved ones, his precious friends, and complained about them. He complained about Auror training, stating he hated it deeply but he had no idea what else to do with his life. He felt aimless. "You're the only constant." Potter told him.
Voldemort kept track of the time.
He stayed inside of his cell for seven months before he lost his ability to contain himself, smashed down the door and brutally killed the guards. He drowned himself in the smell of copper, he missed it dearly. When the (late) reinforcements arrived, Voldemort peacefully returned to his cell.
"I think I could've been a vampire." He told one of the Aurors. When the wizard began to look unnerved, Voldemort grinned and explained. "I love the smell, the taste, the sight, of blood and flesh. I do so miss the battlefield. It was always filled with it."
This basic ass drabble was drawn up from the idea that Harry told Voldemort he was a Horcrux and promised to kill himself if Voldemort didn't surrender. With all of his other Horcruxes destroyed, Voldemort does so to keep a final grasp on his immortality. Harry demands mercy from the Ministry of Magic when they sentenced the Dark Lord, they built a prison on an isolated island designed specifically for him. A number of Aurors stand guard, as Dementors can't be trusted to guard him. Harry visits him often, trying to connect to the Dark Lord and even help him. He hopes with time, Voldemort might change and willingly let go of his sadism, genocidal ideas, and general megalomania. We, of course, know better! :D