WARNING: THIS MAY CONTAIN SPOILERS RELATED TO THE HALO 4 STORYLINE
In the Halo 5: Guardians trailer, Thel 'Vadam can be heard saying “I tell you this, not because I trust you, Agent Locke, but because all our lives are at stake. Because the seeds of our future are sown in his past.” He says “All our lives are at stake” which means that something dangerous is coming, threatening both the Sangheili and the Humans, so much so, in fact, that they are willing to form an alliance to find Chief, who is somehow necessary for their survival against this enemy.
Now that we know they are threatened by an enemy so dangerous, the only thing left to determine is who that enemy is. And it has to be a force so powerful that it would bring the Sangheili and the Humans together in the fight to survive. Now there are only two enemies in the Halo universe that are that powerful, The Flood and The Forerunners.
The Flood isn’t really a possibility, because Chief has already fought and defeated them (Yes, I know there might be more in the galaxy somewhere), and it wouldn’t be original in the slightest if 343i brought them back.
The Forerunners, on the other hand, are extremely likely to be the antagonists, when you look at all the evidence. I will be showing how Halo 4’s Legendary ending confirms that the Forerunners are returning in Halo 5. This will have spoilers about the Halo 4 Legendary ending, so you have been warned!
During the Legendary Ending of Halo 4, the Didact can be heard saying “In this hour of victory, we taste only defeat. I ask why. We are Forerunners, Guardians of all that exists.” Awhile later he says, “I stand before you, accused of the sin of assuring Forerunner ascendancy. Of attempting to save us from this fate we are forced to.” Notice his repeated use of ‘we’ and ‘us’, proving he is talking to friends, or at least allies. He also says “We are Forerunners”, confirming that he is speaking to other Forerunners. He also says calls the Forerunners “Guradians of all that exsist”, which is a possible reason why Halo 5 is called ‘Guardians’. 343i could be using that as a way of saying Forerunners. If you read the books, you will notice that Master Chief has a mysterious connection to and understanding of Forerunner technology (for example, he knows which button to press, even though he doesn’t know how he knows) that even he himself cannot explain, which would explain why the Sangheili and Humans are searching for him. It is possible they need him to defeat the Forerunners.
All this is really exciting, because the Forerunners returning will mean a new war, new enemies, and new planets (Like more shield worlds).
So if 343i does make the Forerunners return, what would you like to see? What locations, weapons, vehicles, and enemy classes would you like them to add?
Thank you for reading, and please tell me in the comments below what you think about this.