Plot device
MacGuffin
An object, goal, or piece of information that drives the plot and motivates the characters while mattering little in itself.
MacGuffin in fiction: 3 works
The coveted Zone artifacts, especially the wish-granting Golden Sphere, drive the stalkers.
The stolen Death Star plans are the goal everyone chases yet matter only as a driver.
The mission to unite two AIs is the goal that drives the crew across the sprawl.