Cleansing the Commonwealth

 is a quest that can be obtained within the Commonwealth, in Fallout 4.

Synopsis
The Brotherhood's mission in the Commonwealth is clear - the acquisition of advanced technology, as well as the extermination of any and all creatures designated by the Brotherhood as abominations. Knight Rhys specializes in the latter, and will frequently assign the Sole Survivor to clear out selected locations.

Walkthrough

 * Speak with Knight Rhys in order to receive orders, which entails traveling to a randomly selected marked location, and killing all enemies marked as abominations. If a location has an interior space, the target might spawn inside. Such is the case with eg. Mass Pike tunnel, where the marker might be at the exterior raider camp, but the target ghoul spawns inside.
 * After effectively killing all of the marked abominations, return to Knight Rhys for a humble reward of bottlecaps.