A/N: Story begins after season 7, episode 6. One (small) change is that Cersei's pregnancy is already near the end - last trimester. Another is that Podrick stayed at Winterfell.
The Pitiless Pit
Jaime nearly stopped breathing the moment he saw Brienne's large silhouette come into view. Why had she come? She should have stayed away, far, far away. All the envoys that had been gathered were guests in the Red Keep. There'd be a banquet first and then a large parley. He didn't approach her immediately so as not to rise Cersei's suspicions. When he finally did speak to her, near the plateau with assorted cheeses, he made sure to be brief.
"I'd expected a Stark to represent the North," he said. "Not you." She looked up with surprise and a smile appeared on her face. "Ser Jaime," she said, "so good to see you too. As to your question: Lady Sansa sent me in her stead," Brienne replied, and as she spotted Cersei who was heavy with child, she continued, "I understand I'm to congratulate you." She did not seem too surprised, Jaime thought, so she must have already heard. He looked away, slightly abashed. "I had not imagined becoming a father again," he replied softly.
"I don't doubt you'll be a good one," Brienne said. His eyes lit up. "Thank you," he said, but then a grim look overtook his face.
"Now, I do need a word." He grabbed her arm a little more forcefully than he'd intended. Her eyes narrowed and her hand went to the hilt of her sword – his former sword – in a reflex. Jaime let her go, making a consolatory gesture with his hands, the gilded and the flesh and bone acting in unison.
"Tonight you should remain near the entrance," he said with a low voice, and when she shot him a puzzled look, he continued, smirking: "Just pretend you're stand-offish. That shouldn't be too hard for you. Say it's customary to your people."
Brienne rose an eyebrow. "Islanders?" she said, "or Northerners?"
"Islanders, Northerners, whatever you wish," he replied. "Just heed my words, will you. For once."
Brienne bit her lip, taken aback, but nodded. "Good," Jaime said and left her to greet another of the guests. All he could do now was hope.
The dinner had been good, Brienne reflected. She had briefly spoken to Jaime's brother who hadn't left his Queen's side and seemed to be determined to avoid his sister. Cersei had spoken to her too. She had been all smiles but had pointed out being pregnant a bit too often for Brienne's taste. Now the food had gone, the wine had been spent and the parley would begin. The great Dragon Pit of old was where negotiations would take place. The Dragon Queen's dragons flew in the air above the great ruin. As the roof had collapsed, they were in sight at all times. Brienne did not see how Cersei could have planned anything. Not with those dreadful beasts so near at hand.
Still, she kept her word and lingered near the entrance. Whenever asked, she said she was fine just where she was, thank you very much. After a while, the official proceedings began, and Brienne was worried she might be called forward. The North would not be the first to be called upon though. As she saw Daenerys Stormborn and Tyrion approach Cersei and her ever present Mountain, she began to feel at unease. Brienne looked around. Jaime wasn't here, she noticed with a jolt. He had been present a mere moment ago. As her eyes overviewed the room, the one they called the spider stood next to her. He'd appeared out of thin air. "A raven from Winterfell, my lady," he whispered in her ear. "I'm afraid it cannot wait."
"I have to stay. I'm meant to represent…" she protested, but he took her hand and said in an even softer whisper: "Your mount is ready and saddled."
Brienne was too shocked to reply. As she left the Dragon Pit, she saw her horse. Ser Jaime held the reins whilst seated on his own fierce war mount. "Come," he said. "We mustn't delay."
Brienne did as he bid her and soon they were on their way. He didn't' speak until they found themselves on a crossroad just outside of the citadel. "Here I must leave you," he said.
"Where will you go? What is happening?" she said, panic creeping into her voice. "Tell me!"
"You will hear soon enough, Brienne," he said, smiling sadly. "I'm to join my forces. Hopefully they will protect me from her wrath. Though Sansa not being present already thwarted her plans."
"What plans?" Brienne called after him, but Jaime did not reply.
"The dragons will be our main concern," Cersei had told him, when she was making said plans. "Other than that, we should be fine. Qyburn is our man." She had smiled, put a hand on her belly, and began to hum The Rains of Castamere. And now he had let Brienne escape, Jaime thought. Cersei had told him not to betray her again, yet here he was. It was not his only betrayal either. He had told Bronn to leave so she could not punish him and he'd gotten the spider to help in keeping Tyrion safe. He had betrayed her a thousand times over, Jaime pondered. She would not forgive. Their child might not live. "I had to do it," he muttered to himself. "I couldn't let her do this, not to Tyrion, and Brienne. Not again."
Cersei was far too fond of wildfire. Like the king he had killed. Jaime had begun to suspect she hated Tyrion more than she loved him, Jaime. She wanted their brother dead so badly; it still shocked him, even though it shouldn't. Tyrion is family, he thought. Though he had killed father and had joined another Queen. Jaime was angry with him too, but killing his own kin? He would never steep as low as that. Perhaps he would have, had he'd gotten his hands on him the night father died. Or the week after, mayhaps. But not now, not anymore.
He would be safe for the moment at least. There was nothing more he could do for Tyrion. Jaime would be with his own, the soldiers who fought and died for him, for his house. Should they turn against him in favor of his sister, he would be lost. He spurred on his horse and rode towards the camp.