The Harvester Empire was the organization founded by the Harvesters and Harvester Queens on their homeworld. As of the War of 2016, the Resistance planned an assault on the Harvesters' homeworld after humanity was elected as their leaders.
The Harvesters and their Queens founded this empire thousands of years ago. They used this empire for evil purposes, primarily attacking other homeworlds, such as the Sphere's. Her species were all but destroyed by the Harvesters, and the Sphere herself was the only survivor. She taught other alien races how to defeat the Harvesters on a hidden planet. However, the Harvester Empire never knew about this planet, and kept attacking others, and the Sphere had to rescue those aliens before the Harvesters could attack.
War of 2016
The IDR Harvester Queen was one of the commanders of the Harvester Empire. She attacked Earth by uprooting it with her Harvester Mothership, including cities, landmasses, and even lava and magma. Once the Mothership landed, it began to harvest the planet's molten core. The Sphere then told humanity about her Resistance's war against the Harvesters. This signaled the IDR Queen that the Sphere has been located.
However, this made matters worse for her. Thomas Whitmore went inside her Queen's Pod with a decoy, and detonated cold-fusion nukes in front of her. Eventually, she was ultimately defeated when hijacked Fighters shot at her back, and she died because of the fatal injuries. This impressed the Sphere so much that she offered humanity to be the Resistance's leaders, which they accepted.