Halo 4: Master Chief is captured on the mysterious planet and forced to fight alien monsters in a gladitorial arena sans his mjolnir armor. After several months, Cortana hatches an elaborate escape plan which involves taking control of a mech and smashing into the arena during a match between John and what appears to be a giant, flood-infected beast. They retrieve John's armor and subsequently escape into the wilds, where Cortana is drawn to a cave opening that leads them several thousands of feet underground. At the bottom of the cave they discover an entrance to a massive Forerunner facility. The facility is re-activated and as Cortana accessess the system, they notice that they've travelled nearly 100 years into the future. Once they locate Earth (using Forerunner sensors hidden throughout the galaxy), they see that there is a second moon orbiting the planet. Something is not right, and Cortana and the Chief make their way to a spaceport and steal a ship. Upon further investigation, it is realized that the second moon is actually a massive alien space station.
Halo 5: They sneak onto Earth and find evidence that humanity has fled to a distant planet about 10 years prior. They decipher the coordinates and head to the new planet. Humanity has changed little, but they've been beaten down and chased across the galaxy. They are tired and in need of a true hero who will inspire them to take back the homeworld. Master Chief and Cortana work with scientists to create the Spartan X program. The Chief leads a Spartan Expeditionary Unit back to Earth to determine the alien capabilities. After infiltrating the alien mothership and stealing some of the alien technology, they are chased down by the aliens (known as the Paracletes), and just barely manage to reach hyperspace. Just as the Humans finish building the flagship "Dawn's Early Light", Slipspace opens up and from it appear several Paraclete battle cruisers. Dawn's Early Light manages to fend off the attack, but is rendered unusable to bring the fight to Earth. Master Chief and Cortana set out for the Elite homeworld to ask for help.
Halo 6: The Elite's, which took a vow of non-violence, had mothballed their fleet of vessels. They only fight each other in combat as a tribute to their heritage and no longer have any aggression toward other races except for self-defense. Master Chief and Cortana return empty-handed, only to find Earth II being attacked by an even larger Paraclete armada. As the Chief battles a 3rd wave of Paraclete Space Fighters in a Human Space Fighter Jet, he gets badly wounded and fades to black. Suddenly, another slipspace portal opens and the Elites come screaming out with guns blazing. After the attack is over, they recover Master Chief's body and use the Paraclete technology stolen in Halo 5 to reanimate him. Master Chief is given command of an Elite battleship, and he leads a dozen more back to Earth to take it back. The Paracletes, expecting that Humans might want their planet back one day, planted a huge nuclear device deep in the planet as a last-ditch self destruct system. Master Chief races to the device, surrounded by an unsurvivable level of radiation. He disappears into the glow surrounding the device and after a few moments his sillhouette appears to collapse. The countdown timer at the surface clicks down to zero and nothing happens, Earth is saved.
