For the event with a similar name, see Home Invasion.
The Invaded House is a small "dungeon" that can be found in Westmarch Commons in Diablo III. The zone opens with a small one-room dwelling, but a wooden walkway in the rear crosses a canal, leading to a larger courtyard with a well in the center.
This area always contains an unmarked mini-event: Elgorath, a unique Revenant Shield Guard, stands over a number of corpses which litter the courtyard. As the Nephalem arrives, other Revenants animate from the bodies, continuing even after Elgorath is killed until most of the dead have been put down a second time. There is no particular reward, other than the usual loot from Elgorath and his victims.