THE TAU EMPIREThe tau empire are a young alien race who have gained lots of high tech when they crashed on tau during the great crisis. While on tau they enlsaved the kroot and the vespids.
THE NECRONS The necrons are an alien race who got wiped out ages ago in the 4th great battle. But know they have come back from the dead. They are back and there better than ever beacause now thanks to there ability we will be back they can't be destroyed unless the whole unit is destroyed. So you are basicly invicible.