At the end we see a Halo installation, it also glows blue which most likely means Cortana is now controlling it, but what really got me was the planet behind it, does anyone have any guesses on what planet it is? Or even what Halo it is.
Also, during the cutscene you can clearly hear something making some sort of screaming noise, the first thing that came to mind was The Flood. ^-^
It could be the same one seen in the advert shown about cheif dying, leading up to release. I think some female astronaut space walking her station near it? My memory is fuzzy
One theory is that the Cortana who you encounter in H5 is one of the Rampant copies that Cortana spit out in Halo 4. And that a None Rampant (or Cortana herself) copy crashed at that Halo Ring and took it over.
One reason for this was the Lack of a Guardian at the Ring and how Cortana was humming, something she never did when you encountered her As chief or Locke
Who knows yet? All I know is that Cortana may have control of an active Halo Ring(s), and that is anything but good. She may even be able to control the other 5 Rings, and that is a pretty terrifying thought.
The next game is going to be crazy.
If that is indeed the sound of the flood, then Halo 6 is going to be an all out war between the factions. (Cortana v Warden v Humans and Arbiter v Remaining Covenant v Flood)