Gizmos are needed to attack an enemy at range. Each Gizmo has a specific use, and can be swapped for another Gizmo during combat.
 
Upgrading Gizmos
Characters become more powerful throughout the game by purchasing upgrades for their Gizmos with the Sprockets collected.  The system offers a layer of customization that is simple yet allows players to re-play the game with different characters and abilities. Maxing out all Gizmos for a single character can only be achieved through multiple playthroughs.