This is a drill

Drakken Laser Drill to be more specific.
This is the already-mentioned mission "The Dig", in which you need to protect a laser drill while it is used to open the gate of an ancient temple and open the way to an artifact, while being attacked by Tal'Darim protoss. (note that this was before Tal'Darim were Sithed up in LotV).
However, at one point you become capable of redirecting the laser drill against enemy units and structures. Since the drill has unlimited range, you can use it to destroy all enemy bases - you just need a spotter, which role can be used by a Terran flying structure. Destroying all enemy units results in fulfilling alternate victory condition.