Snoz is a large three-eyed green-furred monster who sleeps (or at least lurks) under Mechanicsburg. As is allowed, upon hearing the work of the Doom Bell Ringer he emerges on the surface and proceeds to fight for the new Heterodyne against the swarm of Sparks who have descended on the town. More specifically, he destroys a large clank (approximately half the size of Mr. Tock) which goes by the fan-assigned name the Assault Butler, and which is (politely) accosting Agatha on behalf of its unnamed owner. After Snoz is formally introduced to Agatha by Vanamonde von Mekkhan, he goes off to continue smashing things.
Based upon his comments he is younger than the Jägermonsters, having never seen a female Hetrodyne before. He is favorably impressed with her, but regretfully is already in a committed relationship.