Is this cage to keep you out - Or me in?

I've had this image in my head for a long time, and I'm so glad to final let it out. His story is wibbly-wobbley and mostly made up while drawing him, but regardless -
If you enter his abandoned library, his only response is a growl. But little do you realize, a growl is his response to everything. It's the only noise he can make. He was transformed into the violent beast you see before you; cursed to be the dog he is inside.
Then he was muzzled. He can tell no one of his fate. No one will ever know the man that dwells inside.
When he was cursed, a tattoo of a keyhole appeared on his back. It can never be covered or hidden, and shows up even over clothes. He desperately searches for a spell, a key - anything to free him from the curse. That's why he collects ancient spell books, and other powerful artifacts.
Always awaiting - but never daring to hope for - his key.

Media: Watercolours, sepia ink & dip pens, white gel pen.