Balerion the Black Cat
He stretched his limbs after a night's rest, belly still full from the previous day's hunt, blinked his eyes, flicked his ear, and left the darkness of the tunnel.
Many seasons he had prowled the halls, and he knew them well. The kitchens he raided with ease, the mice in the larders and the rats in the stables and walls he hunted. He knew there was always a food source, and more often than not he knew where.
Today, he patrolled his territory. So many younger cats fought one-another, often inflicting injuries, but he had more experience and speed and could beat them all. He regularly did, establishing his dominance. When a stronger cat arose, he would use his knowledge of the castle to lead them to danger and their deaths.
He jumped a wall to a window and crept in. Three young cats and a small human lived there. The young cats were small, frightened things; they shied from him. One would try to fight, but badly; only the human protected them. He disliked the spoilt ones; he had lost his small human, who was still buried deep in the past, but he had been strong. They were weak. They were given their prey, they did not hunt.
Today, a larger human, who smelt similar to the smaller one, was there too, and so the old cat scent-marked and left.
His ear twitched. Other small humans were running around the courtyard, making loud noises and fighting. They were all over the area, their scent pervading the very stones.
In some places, their scents grew stronger, he noted as he prowled a darker corner. Many of the same young scents pervaded it, speaking of many comings and goings; he touched his nose to the wall and it swung open.
He knew of other ways, of course, that led through the walls. He lived in one of them. But this was new.
He sniffed. The young scents led in.
Suddenly, a pattering of human-paws sounded behind him, and he turned. A small one charged around the next corner, moving fast. When it saw the cat, it shooed him away. He moved a short distance, and watched the human disappear as a larger one which smelt odd turned the corner.
He ignored the tall human - they never noticed him - and poked the wall again. It opened; he sniffed, took a step-
But this strange-smelling human was moving, he could hear, and the human was next to him. He shied away, hissing, and left, leaving the human with the thin pointy metal to do the sniffing.
He would investigate another day. There was a scent of tomcat around the next corner, an arrogant ginger tom he recognised.
The old black cat chased the younger to the kitchens, then hid, leaving a serving boy to kick it and break it's leg.
He returned via the room with the spoilt cats again. The larger human who smelt like the smaller had gone, but there was another in her place. A the cat watched, the large human who had interrupted him entered too, and spoke to the other large human.
While they did so, the cat snuck into the room and loosely bit one of the nearby kittens around the neck, before scent-marking it's pelt quickly. It's mewl was pitiful. It knew he was dominant, and he snuck out to hunt immediately afterwards, satisfied.
...
Elia Martell and Rhaegar Targaryen's daughter, Rhaenys, had a little black kitten, called Balerion, that she called out for as she was dragged from her hiding place to her death. Fourteen years later, Arya Stark is chasing cats, but never catches an old black tomcat with one ear and a thousand tricks. She was told that "he was the real king of the Red Keep." He once snatched a roast quail from Lord Tywin's hand. After another year or two, King Tommen complains that Ser Pounce, one of his new kittens, is afraid of the old black cat that roams the castle. Cersei says they haven't managed to trap it, but they have tried.
I cannot be the only one to have connected them, right?! I absolutely love that kind of subtlety in a story; it's not mentioned, but if you look... It's there.
So! Here's his POV! A short one, but it uses one of my theories and will act as a precedent for the next King's Landing chapter. There were clues there, yes there were...
Also, Shadowcats and Direwolves has just been posted, so please go check it out! I intend to update this one more regularly than that, but that one should be more focused on just the one character... Hopefully it'll go down well!