There will be four endings! 1] Destruction Master Chief decides to destroy all synthetic life, including his new ancilla, but all the Prometheans, Sentinels and even remnants of the Forerunner civilization will be destroyed, as the Librarian and the Didact. Master Chief will die unless you have completed a certain amount of achievements throughout the reclaimer trilogy. 2] Rule the Prometheans Master Chief will rule the Prometheans and become the new Didact, he will instead rebuild the galaxy for the Humans and destroy the extremist remnants of the Covenant, securing a new life for all sentient life in the galaxy using his Prometheans to protect it from any threat and eventually the Flood if the need will arise ever again. 3] Everything Synthetic Everything turns synthetic and stopping the huge invasion of the Prometheans against the Humans and other sentient species in the galaxy and will live under the rule of the Didact and the Librarian. Humans will be assimilated and become Prometheans just like their ancestors in the times of old. 4] Refusal The Chief refuses any of the endings and thus the Prometheans destroy Earth and humanity will be scattered once more. The few remnants of the current human civilization will leave the ruins for the Humans that will be saved again from the Librarian's secret facility and will ultimately defeat the Didact and the Flood in the future. In any of the endings the Halo rings will be destroyed.