This is a personal illustration. A lot of the art I do can tend to lean a bit more serious, so I wanted to try and aim for something more whimsical but still gnarly.
I like to imagine he would wander dungeons, dragging the chain around behind him with his back bent. When an adventure comes along he starts breathing heavy and worbling toward them on his little legs. He would swing the flail by whipping his entire contorted body around - probably creating more of a danger to himself than anyone else.
I also love the thought of him having this little useless T-Rex like arm that's just sorta flapping uselessly while he wildly wiggles and throws himself toward the intruder.
I made a gif of the images construction from old Photoshop files and layers, its not quite a time lapse but you kinda get an idea of went into it which is I think is fun :)