Delta Rana IV is a planet whose Federation colony was wiped out by the Husnock, leaving only one house standing.
Delta Rana IV is the planet visited in The Survivors, where the Enterprise answered a distress call from a Federation colony. The crew found it devastated and lifeless apart from a single house and its garden, home to Kevin and Rishon Uxbridge.
The colony had been destroyed by the Husnock. Kevin, secretly a Douwd, had refused to fight, then in his grief wiped out the entire Husnock species. He had recreated Rishon and the house, and he chose to remain on the planet alone.