"Ned!" Robert's roar echoed through the great hall "What has gotten into you? You detained my wife and her brother as well as all the Lannister soldiers"
"Aye, Your Grace. And it took all my inner strength not to kill them outright. They violated our sacred traditions of Guest Rights. They tried to kill my boy, Bran. The Kingslayer pushed him from the top of the Broken Tower when the boy saw him with the Queen. If not for that foreigner I told you about, Lady Arabella, using her magic to catch him. He'd be dead"
"So it's true then… people were talking about a sorceress in Winterfell" he said, trying to bottle up his rage long enough to make a coherent speech "You said your boy saw Cersei with the Kingslayer. What were they doing on top of that tower?"
"Robert…" Eddard sighed "there's no easy way to say it…"
"Then just say it Ned" roared the King again, somewhat suspicious what it could be "Out with it, now!"
The nearby servants and nobles flinched at the strength of his voice. He may be fat, but even in this state many believed Robert still to be a menace. Eddard took a deep breath before saying.
"They were having sex."
"THEY WHAT? " roared the King before smashing a table into two with his warhammer "THAT WHORE! BRING THEM HERE NED, BRING THEM NOW! I WILL TAKE THEIR HEADS"
___________________________________________________________________
When the King's wrath had calmed down enough for him to be able to think straight, no small part due to the wine he drank in the meantime, Jamie and Cersei were brought before the great hall. Robert sat on the Throne of Winter, with Eddard standing on his right. Behind him were the Starks and on both sides of the hall several nobles from the North and a few from the King's party.
The accused were still wearing the same clothes they had on them on the Broken Tower. Jamie wore nothing more than a long shirt and Cersei had a half-torn dress. The Kingslayer looked around with his same smug smile of always, as if what was going on were the most normal thing ever. Cersei, however, had a mix of fear and anger. Anger at Robert, anger at the Stark boy, anger for being caught and fear. Fear for what was to come.
Eddard's voice broke the silence.
"We are here for the trial of Jamie of House Lannister and Cersei of House Lannister for the crimes of murder and adultery" He said with a tone colder than ice. "Before proof is brought before the crown. Do the accused have anything to say in their defense?"
Jamie said nothing, just glared at Eddard. Cersei, on the other hand, snapped once again.
"Robert, what kind of King are you? You vassal arrests your wife and a member of the Kingsguard, throws them in the dungeon and you do nothing?"
"Enough woman!" growled Robert "your games will not save you now. Say what you want in your defense or shut up!"
"I have nothing to say" she continued "Your friend Ned Stark framed us and he has no proof."
"My boy saw you two having sex before the Kingslayer pushed him out of the window. And, just by looking at your clothes, there's no need to think much to understand what you were doing there."
"Lies!" Cersei shrieked "the clothes were damaged as we were ruthlessly dragged away by these northern savages. As for the little Stark, he'd say anything his father ordered him. He just wants to cause a rift between you and my father, Robert. To weaken you so he can take the throne for himself"
The northern lords roared and cursed at the suggestion. Steel was drawn, but the Lord Paramount of the North was able to calm things down after a while. Robert only glared at his wife, a second away from blowing up and beating her up to death. Once there was order in the hall, he spoke.
"Where is the Sorceress? The one that saved your boy?" he asked Lord Stark.
On Eddard's gesture, Arabella moved from the gathered lords towards the center of the hall, took a bow and spoke.
"Your Grace, how may I be of service?"
"Arabella Slytherin, yes? Ned told me about you and it seemed it wasn't the wine speaking when he said you have powers. Tell me, did you see the Kingslayer pushing Brandon Stark off the tower?"
"No, Your Grace. When I arrived, Bran was already mid-fall and I focused my attention on breaking his fall."
"See?" said Cersei, jumping on the situation and trying to cause chaos "Even this Sorceress didn't see us. Eddard Stark is lying"
"I'm sorry, Your Grace" Arabella raised her voice "I didn't see him pushing him aside, but I saw when the Kingslayer killed one of Lord Eddard's guard and used the man's sword to try and kill Lord Stark"
"It is true. Not only did she save my boy's life, she probably also saved mine."
"She surely did," said Jamie with an even bigger smirk.
A guard punched him across the face, silencing him. Arabella glared towards Cersei before continuing.
"Your Grace, if you'd wish, I have the means of obtaining a confession from the accused"
She was ready to use the cruciatus curse on them. In fact, nothing would make her happier at the moment. It's not like the Ministry of Magic would show up to arrest her for using it anyways. And if they did, she'd go home, so no problem.
"Lady Slytherin, I will not tolerate torture under my roof" said Eddard somberly.
Well… no cruciatus then…
"Not to worry, Lord Stark. I don't need to torture anyone. I have a way of bending one's mind to my will. It's not permanent, but it will allow me to provide you with the proof. If I tell them to tell the truth and nothing but the truth, they'll have no choice but to do exactly that. "
"No!" shrieked Cersei "Robert, you can't possibly be serious in letting a Sorcerer, a sinner, cast a spell on us. That's a straight slight against the Seven!" Not that Cersei cared. She wouldn't hesitate to use it if she was on the other side. Some southern lords tried to agree, but were cut off by Robert's decisiveness.
"Go ahead, let's see what you've got, Sorceress"
Arabella picked up her wand and placed it in front of Cersei's face as she shrieked and tried to break away.
"Imperio"
As if her wand had sprayed perfume, a faint mist enveloped Cersei and soon her struggle ceased. Jamie was horrified to see what had happened to his sister, but his reaction was cut short as the same happened to him.
"Now, you will answer all the King's questions and you'll say the absolute truth to him. Do you understand"
"Yes" they replied in monotonous unison.
"Your Grace, I'd advise you to direct your question to one of them at a time and to try and make simple questions that involve little explanation. It will put less strain on the spell"
"Fine" he growled, though Arabella could sense a hint of fear in the King's voice "Kingslayer, did you try to kill Brandon Stark?"
"Yes."
"Why?" he asked, even more angry.
"Because Cersei asked me to do it. He saw us, so he needed to die. The things we do for love."
Robert threw his cup on Jamie's face, but he just took the blow before looking forwards with no reaction.
"So it's true!" he roared "You were fucking your sister?"
"Yes"
"Was it the first time?" he asked Cersei
"No" she replied.
His anger boiled over again and he punched Cersei in the face two times before Eddard and Arabella pushed him back.
"Your Grace, the spell will fade if you keep doing this"
Robert was surprised to see a woman touching him with such fearlessness and power. She reminded him of Lyanna. Were it not for her blue eyes one could say they were very similar. This thought brought him a mix of sorrow and lust, both helping him calm down.
He returned to his seat and asked again
"For how long had this been going on"
"For as long as we are married and even before" answered Cersei.
He glared at them once again, thinking about how many times they could possibly have done it. It was true that he spent a lot of time drunk or whoring around. Cersei had plenty of opportunities to cuckold him. It was then that a thought crossed his mind.
"Cersei… our children" he growled "Are our children mine?"
"No"
Amidst the gasps from the crowd, Robert picked up his warhammer and before anyone could intervene, he brought it down on top of Cersei's head. It exploded with a sickening crack, sending blood and brain matter all over the hall. Then, with an even more ferocious strike, he hit Jamie Lannister through the chest, caving his ribs in and making the bones pierce through the other side. Arabella was shocked at what she saw and many ladies fainted from the scene.
Then, Robert dropped his hammer and left the great hall with only Eddard Stark being brave enough to go after him.