This spell enchants a pile of sticks, paper scrolls, scraps of cloths, or some similar set of objects to become animated, amassing into a shape similar to the body (a “marionette”) of the caster. For as long as the caster wills this spell to continue, the marionette will mimic the caster's every move exactly.
The marionette will mimic a gross approximation of the original caster only, and will mimic movements that involve precise actions of fine motor skills only with a vague imitation. This, it is not likely that it will be able to wield a weapon, perform a ritual, or pick a lock. It is also a very flimsy construct, and will crumble if it significantly impacts a wall, is struck by an object, or is otherwise disturbed.
The marionette lasts indefinitely, and is only limited by the lifespan of the objects that it's made of (paper will disintegrate in fire, dissolve when wet, etc), and how long the caster wills it to exist. The caster may cast spells, perform complicated actions, concentrate on other things, and even sleep while the marionette exists.