The faction was first introduced in the RTS spin-off Halo Wars 2. In that game, the group is led by Atriox, the snarling foe who managed to capture the Ark, the massive Forerunner facility first introduced in Halo 3 that can construct new Halo rings as needed. With the Ark under his control, Atriox planned to create a new Halo ring with which to vanquish his enemies. But the end of Halo Wars 2‘s main campaign and its DLC left Atriox’s story unfinished, Installation 09 beyond his grasp as it went into slipspace without him. It remains to be seen whether he’ll play a part in Halo Infinite, although the trailer does tease that Escharum fights “to honor the will of Atriox.”
Atriox is a master strategist and an effective leader, but he’s also ruthless. Whether he wants power for its own sake or has another motive behind his mission is unclear, but the plan is clearly working since the new Halo ring is already “under Banished control,” according to Escharum.
With his scarred face, grandiose manner, and probably a wicked swing with a gravity hammer, Escharum will bring the pirate philosophy of the Banished to bear against Master Chief in Halo Infinite. But the trailer teases that he’s not working alone. Escharum says that “the Harbinger and the Banished share the same goal” under Atriox and that they’ll soon capture a mysterious location known as “the Auditorium.” The Harbinger is a brand-new term in the Halo universe that may point back to the events of Halo 5: Guardians.
It’s possible that Cortana is the Harbinger. A human-made AI and Master Chief’s partner in the first four Halo games, Cortana created a new faction known as the Created, sparking a violent AI uprising at the very end of Halo 5 that left humanity’s forces in disarray. Is she the Harbinger who’s recruited the Banished to her cause?
The word “harbinger” implies this individual is bringing or predicting something that’s to come, but the context is too vague to really speculate on. Either way, 343 has said that Halo Infinite isn’t a total reboot. Even if it isn’t a numbered sequel, the game will still follow the events of Halo 5.