Mogget

Mogget is one of the characters from the Old Kingdom trilogy by Garth Nix, like the Disreputable Dog. For the most part, he's bound in the form of a small white cat, with a collar of magic around his neck, bound by one of the bells that the Abhorsen use to control the Dead. He's bound in punishment for not supporting either Orannis, a great enemy, or those who in turn bound him.

"The cat twitched and turned its head ever so slightly to look at her, revealing bright, green eyes.

'Hello, puss,' croaked Sabriel, coughing as she staggered once more to her feet and walked forward, groaning and creaking with every step. She reached down to pat the cat and froze - for, as the cat thrust its head up, she saw the collar around its neck and the tiny bell that hung there. The collar was only red leather, but the Charter-spell on it was the strongest, most enduring binding that Sabriel had ever seen or felt - and the bell was a miniature Saraneth. The cat was no cat, but a Free Magic creature of ancient power."

Whenever the collar is removed, that creature within Mogget is released, and he tries to get revenge for his years of servitude by attacking the Abhorsen. However, at the very end, Sameth releases Mogget from his bonds to give him a free choice.

"Bells rang, Yrael sang, Kibeth barked, Astarael mourned. The silver spread, and Lirael moved in closer and raised the weapon Sam had made for her from blood and sword and the spirit of the Seven in the panpipes.

Orannis spoke then, in bitter cutting tones.

'Why, Yrael?' it said, as the last of the dark gave way to silver and the shining sphere of metal sank slowly to the ground. 'Why?'

Yrael's answer seemed to travel across a great space, words trickling into Lirael's consciousness as she raised her sword still higher, body arching back, preparing for the mighty blow that must cut through the entire sphere.

'Life,' said Yrael, who was more Mogget than it ever knew. 'Fish and fowl, warm sun and shady trees, the field mice in the wheat, under the cool light of the moon. All the - '"