Disclaimer - None of this is mine. All credit goes to the wonderful J.K.Rowling.
This is a one shot about the day that Bella joins the Death Eaters.
Bellatrix Black walked quietly through the Black family manor at Number 12 Grimmauld Place. The house was beautiful, as it had always been. All manner of dark objects lined the walls. There were the heads of all the former house elves mounted on the wall, the magnificient painting of her Aunt, and so many trinkets that could be used to hurt, maim, torture, and kill unsuspecting victims that it made Bella tingle with delight. Coming here was always a treat, but this time would be different. This time she had come to try to talk sense into her younger cousin Sirius, once again.
It was now or never. She would try to reason with Sirius one more time. He was turning fifteen this week and Bellatrix felt that it was high time Sirius proved his worth as a Black and showed his loyalty to their family legacy and joined Bellatrix in becoming one of the Dark Lord's most trusted followers.
Death Eaters. That though made Bella shiver with excitement. To think that she, Bellatix Black, would join the ranks with those she held in highest esteem.
"Sirius Black," Bella said as she opened the door to his disgustingly decorated bedroom. A black haired, brown eyed boy looked up at her from his Quidditch book, frowning.
"What do you want, Bellatrix," Sirius asked her curtly.
"I want you to show our family that you are a true Black. Come with me. Join the ranks of the Dark Lords most feared and honored followers. Become a Death Eater."
Bella paused and awaited his answer. Surely he would agree. Surely Sirius would see the error of his ways. There was no greater joy than inflicting pain on another, seeing their features contort in pain. Bella had never known such please before. Surely Sirius would agree once Bella found his some poor unsuspecting Muggle he could practice on…
"Sorry, not today Bella." Bellatrix was afraid that she didn't hear him right at first, but catching sight of the huge Gryffindor banners and those horrid Muggle posters on the walls, she knew that she heard correctly.
"What is more important than the Dark Lord and serving him?"
"Well for starters Quidditch, practical jokes, pranking Snivellus, and – oh I dunno – how about plotting Voldemort's demise?" Sirius went back to reading his Quidditch Through the Ages as if what he had said wasn't the foulest, most retched thing that Bellatrix had ever heard. Now she finally understood what Aunt Walburga meant when she said Sirius was a blood traitor.
"Is this the path you choose? You would rather follow that fool James Potter and Albus Dumbledore around like a pathetic little lap dog?" Bella shrieked at him. Sirius smirked at the statement.
"Even to death? We will win cousin, there's no denying it. Nothing can stop the Dark Lord. Not even your precious Dumbledore."
"He'll be stopped. And I'll be there when he is." Bellatrix laughed her high pitched, insane laugh.
"You'll be dead long before that, my dear cousin. You won't stand before the Dark Lord and live."
"I'm not afraid if that was your intent, Bella. If I die beside my friends fighting for what I believe in, it would be worth it."
Bella's eyes flashed dangerously and she spit on Sirius's shoes. Sirius just stared back very calmly. A hand fell on her arm just as Bellatrix reached for her wand.
"Not now Bella, dear," her Aunt Walburga said. "You'll be late. I'll take care of my son." Bella smiled devilishly. Her Aunt was a force to be reckoned with knowing no limits or boundaries.
"Yes, Auntie, I'll be leaving now." She gave Sirius one last glance. What Auntie Walburga was going to do to Sirius, Bella didn't know, but from the look on her face it seemed like Sirius's survival was in jeopardy. Bellatrix wanted to know what was going to happen to her cousin, but the lure of Voldemort was too strong.
The green fire rose around her, licking at Bella's black cloak and wild black hair, yet nothing was burned and Bella wondered for an instant what it would feel like to be on fire. But soon she stepped out of the grate onto the other side.
A group of Death Eaters parted and a man walked out from behind them. He was tall with red eyes and slits for nostrils. Long thin fingers grasped a wand, a wand he inflicted more death and pain than any other had. This man was Lord Voldemort, and Bella though he was the most beautiful thing she had ever seen.
"We have been expecting you, Bella," he said.
The wand raised up and then came down on Bellatrix's arm. Underneath it appeared a snake protruding from the mouth of a skull. It was the dark Mark. Bella laughed in delight. This was the moment she had been waiting for her whole life.