Ender, now 10 years old, is promoted to Command School on Eros after a brief respite on Earth. After some preliminary battles in the simulator, he is introduced to a former war hero, Mazer Rackham. From then on, Ender participates in simulations created and controlled by Mazer. As the skirmishes become harder, he is joined by some of his friends from the Battle School as sub-commanders. Despite this, Ender becomes depressed by the battles, his isolation, and by the way Mazer treats him.