Dr. Snap is the main antagonist of Dragon Quest Monsters: Joker. 
Dr. Snap
He's the operator of the Monster Scout Challenge, which means he's in charge of assigning the quests to the various scouts, the Hero included. He also invented the Scout Ring, the artifact that lets scouts recruit monsters.


In an extreme attempt to bring ultimate harmony between monsters and humans, he opened a portal to the Dark World using the Incarnus, recruitment ring and the dark orb and transformed himself into a bizarre creature known as Dr. Snapped. The final battle the hero has to defeat this monstrosity.

Dr. Snapped

Dr. Snapped is the name of the monster that Snap becomes after opening the portal to the world of darkness, it's an obtainable monster but only through synthesis in DQMJ and DQMJ2 which requires a Captain Crow, Darkonium Slime, Orgodemir and Rhapthorne 2.