This was intended to be a headcannon on one of my Facebook pages, but I do quite like it, so tada! Here you go! Be warned, it's kind of violent xD
Bellatrix and Tom Riddle
"Well done Bellatrix, that was... exemplary," he said softly into her ear and she trembled at his closeness to her.
Her first kill. The first time she had complete control over a life, and she had ended it. She was still buzzing and her Lord, her wonderful Lord was praising her, for it had indeed, been a wonderful way to kill.
Never charge right in, no, where would be the fun? The others she had been training with had mocked the muggle, prodded him the cruciatus curse, but none of them had been able to kill their muggle. Until Bellatrix.
Tom had been watching them fail, over and over again, but there was something about this one, this woman. She had skill, unlike so many of the others. It was like she knew what spell they would cast, like she knew their every move... even he had trouble duelling her. She was yet to win against him, but he was yet to lose to her.
He had dismissed the others, sent them away not wanting to look at their failures but when Bellatrix stepped up, faced with four different muggles, she put on a show, a magnificent show.
It would have been so simple to kill them, end their worthless lives but Bellatrix was a sadist. She, like him, wanted to watch the light leave their eyes.
The first one had died after several small spells that caused blood to erupt from over his body and his nose to fall to the floor. He had laughed at her... 'innocent' way of killing that one.
The second and third were killed together, as she shot a spell causing their bodies to combust and she got to watch them die from the inside out, their faces twisting in agony, bloodcurdling screams echoing through the room and she stood in the center of it, cackling.
The fourth man was different. Bellatrix seemed to have something saved for him. She threw him a short cruciatus curse, circling him, glaring at him, whispering threats that caused him to tremble.
She laughed again whilst holding a long cruciatus on him, his screams fuelling her laugh.
When she was breathless power, only then did she cast his curse, the killing curse, ending the man's life. When this had been done, he entered ready to congratulate her.
"Well done Bellatrix, that was... exemplary," he said softly into her ear and she trembled at his closeness to her. "You are finished. You have done it. You are to join my ranks, be my right hand man, the one I trust and rely on. The only one worth anything." he said softly and she closed her eyes, stiffling a moan at his low voice.
He took her hand and placed a kiss there and she nearly fainted, but her eyes snapped open when a searing pain shoot through he left arm, but it was a good pain, it made her laugh, cackle.
When it ended, she looked up to him, her dark eyes twinkling and he said softly, right in her ear, 'mine."
Oooh, that was weird to write! I don't know if it makes sense, s'abit odd, but aren't Bella and Voldy a bit odd? Again, a long headcannon, but sshh! I don't do short, I just don't do too long! xD