The first part contains torture. If you don't want to read it, skip the part till the line (break?).
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The inside of the cell was quite larger than he expected. Umbridge was lying in one corner of the cell. A table present near the door of the cell. On the table, a wand and several other objects were present.
The Dark Lord sneered at the prone body of the witch and sent a "Rennervate" at her.
With a startled gasp, the witch woke up and started looking around the cell. Finally, her eyes settled on the two wizards at the centre of the room and started shrieking.
"WHO ARE YOU!? WHERE AM I!? DO YOU EVEN KNOW WHO I A-"
Sneering even more at the witch, the Dark Lord hit her with a strong crucio.
Umbridge started screaming and crying from the pain.
As soon as her screams started, a pleased expression came over the Dark Lord's face.
The man was enjoying the torture. Tom wondered how long it would last.
After a few minutes, the Dark Lord cancelled the spell and went towards the witch. He stared at her coldly for a minute, before he asked her, "Do I know who you are, yes. A pathetic, soon-to-be dead witch. Let me ask you, do you know who I am?"
Even his voice changed as he talked. The velvety, warm voice which Tom was accustomed to, changed into a cold, deep voice.
Umbridge's face went pale as she realized who the person in front of her was. "L-lord Had-des?"
"Yes." He sneered and flicked his wrist.
The sound of snapping of a bone was heard in the cell.
The toad started sobbing and pleading even more.
The Dark Lord smiled manically at that and broke five more bones. He then snapped his fingers and yelled, "Kreacher!"
An old looking, wrinkly house-elf popped inside the cell.
"How can I help you, Master Hades?"
"Bring me the Black Quill from the Red room."
"Yes, Master."
The elf went and came back seconds later with a black box.
The Dark Lord took the box from the elf and dismissed Kreacher. He then took out a black quill from it and kept it in front of Umbridge.
The toad's eyes went frantically from the Dark Lord to the quill.
He smiled sinisterly at the witch and turned to look at Tom.
"What do you wish her to write, my dear?" He asked in a sweet tone, as if asking which flower he wanted.
Tom gulped. 'Huh. This is it. My first intended torture.'
He looked at the toad. The woman had scarred him for life without an ounce of regret. No, the sick woman enjoyed it. She made his fifth year hell. Tom had vowed to make her pay for it. He will make her pay for it.
"I must respect my betters." He said in a cold voice.
The man nodded and looked back at the woman.
Sneering, he spat at her, "You have two options, bit*h. Either you do this willingly or I'll force you to do it. And I can confirm that the second option will be more painful."
Sobbing, Umbridge said, "I-I'm s-sorry, my Lord! I swear I-I haven't done a-anything. P-please spare m-me, my Lord. I-I'll do anything, p-please, m-my Lord."
If anything, it enraged the Dark Lord even more. Furious, he spoke, "Your Lord! You don't deserve to even be in my presence, let alone call me your Lord! You disgust me! You vile filth! Crucio!" He tortured the witch for few more minutes before be stopped the spell and said, "Imperio!"
With that, he forced the women to write the lines for over half-an-hour.
Tom noticed that the lines did not only appear behind her hand, but over her whole body.
Umbridge was shaking, wailing and a bloody mess when the Dark Lord ended the spell. Blood and filth was all over her body.
Immediately, she fainted.
The Dark Lord once again revived her and pressed his boot on her hand. Tom winced, hearing more breaking noises.
With a wave of his hand, the Black Quill flies into the Dark Lord's hand, who vanishes it then.
Tilting his head, he asks quietly, "Do you know, Dolores, why are you here?"
The witch only shaked her head frantically.
Smiling nastily, he gestured Tom to come forward and said, "Remove the mask, sweet."
Quite surprised, Tom removed the mask.
Umbridge squints at him, clearly not able to see properly. Recognition crossed her features.
"Y-you!"
"Yes, me." Tom drawled.
"Wh-what? W-why? He's a M-mudblood, my Lord!" She yelled.
Suddenly, she was once again put under the Cruciatus Curse, this time more painful. He then used a blood-boiling and some other dark curses on her.
"You will respect him, Umbridge!" The Dark Lord spat.
The witch could only nod fearfully, tears and blood falling down her face.
Looking at the toad-like woman in disgust, the Lord turned towards Tom.
"Have you ever used any Dark spell, Tom?"
"No, my Lord. I only know the theory."
The Dark Lord looked happy and said, "Well, my prince, this is a perfect opportunity to teach you the spells then!"
After that, with Harry's guidance, Tom performed many different spells on the woman, ranging from slightly dark spells like a nightmare inducing one to the unforgivables.
By the end, a literal bloody mess remained of the women, and it was only Harry's magic which was keeping the women alive.
Looking at her made Tom slighly nauseous.
Also, the Dark Lord looked more and more excited as he taught Tom different spells. Yes, he was a really good Professor. It was quite clear that he was enjoying this.
But the man also started flirting with him in between the teachings!
"Now darling, you have only one Unforgivable to master. I hope you can do it?" Tom shivered at the velvety voice. Now, the man was quite literally plastered behind his back, his hands sliding up and down his arms, and whispering in his ear. He could only nod at this point.
"Hmm. You know the incantation and the wand movements right, sweet? Remember, you have to mean it. Focus on your intention, your want to kill her. Not on the hatred. It will only complicate the matter. Concentrate on your desire, darling."
Tom leveled his wand at the woman. He focused on his desire to kill her and on the magic in the air.
"Avada Kedavra"
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When the duo exited the dungeons, Tom saw the unknown man reading some tome in the living room.
Noticing their presence, he stood up and asked, "What to do next, my Lord?"
The Dark Lord sat on one of the couches, with Tom on his side, and leaned back.
"The next attack is tomorrow at seven right?"
"Yes."
"Hmm. The charms will hold on till then. Who is tomorrow's target?"
"Walden McNair."
The Dark Lord sneered and said, "Tell others not to finish off the scum tomorrow. We'll fix another date. Use the bit*h downstairs."
"Alright."
"Who are the ones in charge of the attack tomorrow?"
The man gave the Dark Lord some papers, which he immediately started to go over.
"You can remove the mask, Moony. And please bring a nutrition potion for Tom here."
The man, Moony apparently, removed his mask.
The man had light brown hair and green eyes, though they were different from Harry's. He was quite tall, at least 6'3", and had some scars across his face.
Tom wondered why he hadn't noticed his hair and eye color before. The man was wearing a half-mask too.
The man seemed to know what he was thinking and said, "The mask has various charms on it to protect our identity. The most basic ones are a variation of the notice-me-not charm." He had a rather kind voice for someone who had just participated in a murder.
"Oh. Thank you, Mr. Moony."
The man chuckled slightly and said, "Please call me Remus or Moony, if you will. I'm Remus Black."
"I'm Tom Riddle. Are you related to Harry's godfather?" He asked curiously.
The man smiled softly and said, "Yes. He's my husband."
"Oh."
The man then went into some room and returned with the bottled potion.
Harry, the whole time, was engrossed completely in what was written on the parchment. He had a quill in his hand and was writing something frequently on the sheet. It reminded him of Harry grading the assignments at school.
School. Hogwarts. He had almost forgotten about it. Only hours ago he was there, complaining about stupid brats and fussing over assignments. And now, here he was, sitting beside the most dangerous Dark Lord in decades with his godfather's husband, who happened to be a Reaper, after murdering someone. His first murder. It was so surreal.
He also noticed the giddiness and the rush of power he felt. Untill now, he was so caught up in the thought that he murdered someone, that he did not notice his body's reaction. He could also sense the powerful waves of Dark magic coming from Harry and Remus. Pure dark magic was flowing in his body. He had never experienced such tremendous force of power before. He was feeling lightheaded from the rush of power.
Suddenly, he started giggling. He had never felt so great before!
Harry looked up from the parchment and grinned at him. He gave the sheet to Moony and took the requested potion.
"Here, drink this, Tom. In this state, you'll not be able to eat anything. "
He blinked owlishly at the man, before drinking the potion, grimacing at the taste. He again started giggling uncontrollably.
He had read about the effects of Dark magic on a wizard. Especially using it first time. But experiencing it was a whole new different thing. It was glorious.
The Dark Lord spoke with Moony for sometime, after which the man left.
Harry then stood up from the couch, placed his arms under the Slytherin's knees and arms, and lifted Tom in his arms.
Tom giggled even more at that.
"Huh. I should've not let you use so many Dark spells today. My fault. Come on, little snake, time to sleep."
"You're so strong. How are you able to lift me up?" He felt drunk now.
The man smirked a bit and said, "Because I'm strong."
Tom could do nothing but giggle at the man.
Finally, they went inside a room, which had a big king sized bed.
Harry settled him on it and waved his wand over both of them to change their clothes. He then went to the other side of the bed and sat on it, leaning on the headboard.
"Wait! We aren't supposed to do this!"
Tom exclaimed.
"Do what?" The man asked, raising his eyebrow, clearly amused at Tom's drunk-like-state.
"This! Sleeping together! You haven't even kissed me yet! This is not proper!" He blushed and said.
The man laughed loudly. Finally controlling himself, he said, "Darling, killing someone isn't proper too, but we did it anyway. So I think we're beyond that. Also, we're only sleeping now. Nothing improper." He then smirked lecherously and said, "Unless you want to."
Tom blushed even more and squeaked, mortified, "N-no!"
The man then looked hurt and said, "W-wait. No? Like ever?"
Tom panicked, thinking he had really hurt the man and said, "No! Not like that! We can! But- but not now!" His face was burning with embarrassment now.
Harry, who couldn't help it anymore, doubled up, laughing loudly now.
"Hey! You're teasing me! Meanie!"
That made Harry laugh even more. His stomach started to hurt by laughing so hard.
"I couldn't help it, sweet." He said between his laughs.
Finally when he stopped laughing, he laid down beside Tom, putting an arm over him and bringing him close.
"Sleep, my sweet. It's late now. Plus, you are exhausted now. You've used a lot of magic today. "
"Alright." Tom mumbled, finally feeling tired.
"Good night, Tom."
"Good night, Harry."
With that he fell asleep, exhaustion taking over him, snuggling closer to the Darkest Lord in centuries.