Halo 4 is the start of a new saga in the Master Chief's story. This saga is known as the Reclaimer Saga. At the end of the legendary mode of Halo 3 we see Master Chief Petty Officer John-117 orbiting a planet and hear him say to Cortana "Wake me when you need me". Well now is the time to be needed. The game starts where you last left off in a torn in half ship orbiting a planet around four years after the events of Halo 3. John wakes up to Cortana screaming "John I need you!" This creates the beginning of a new saga. In Halo 4 we see a new breed of enemies called the Prometheans. The Prometheans are AIs created by the Forerunners to protect a planet. Unfortunately you're seen as a threat. However despite being made by the Forerunners the Prometheans have a much darker and more sinister plot. Also aside from the Prometheans, Cortana is turning rampant and has begun to turn on the Master Chief. As a new twist, the Master Chief will be working together with the Spartan IV's the replacements to the Master Chief.