: The E3 Demo showed team Osiris at the Battle of Saunaion. They are looking
: for the MC before he can activate a guardian, they even stop and scan the
: MC's discarded auto rifle. The Arbiter even mentions in the cinematic that
: the MC is there.

: Problem is, in the final product, MC is not on Sanghelios, he is already at
: Genesis.

: That got me to thinking. Usually at E3, they show off earlier levels in a
: game (Halo 2: New Mombasa, Halo 3: Sierra 117, Halo 4: Infinity).
: Although, the Halo 4 demo is about halfway through the campaign. The
: Battle of Saunaion is near the end of the game. The Halo 5 Demo is 12th
: out of 15 missions.

: Could they have scrapped a later mission, and reworked the script to where
: Osiris is activating the Guardian, and not the Chief? It looks that way.
: The missions on Meridian now play out similar to the E3 version of
: Saunaion: we are searching for the MC, look for clues in town, and meet
: the Warden (for presumably the first time in E3 Sauraion, and Meridian at
: launch). In both the E3 demo, and the final Meridian mission, the Warden
: states that the MC can pass, but we cannot. I don't recall if he restates
: that in the launch version of Sauraion or not.

: Therefore, in the E3 version, there would not have been human collateral
: damage from the MC using a guardian to escape Sanhelios. By moving the MC
: to the Meridian mission, there are now innocent civilians killed, and the
: MC and Team Osiris both acknowledge this.

: This would also explain all the #huntthetruth and "traitor" teasers
: that didn't really play into the story at all.

: TLDR: I think the battle of Sauraion was earlier in the game. Story was
: altered, and Meridian was created at the 11th hr to fit the same role that
: Sauraion originally held (MC escaping on a Guardian, Osiris' first brush
: with the Warden.

It's certainly *possible*, but game demonstrations for trade shows in general, including Halo's, have always been about presentation first. They might have just stuck bits from other levels into the demo level because that way they gave more plot without spoiling the late game; Sunaion may also have been more feature-complete at the time and thus it was easier to spin it off and polish it up as opposed to an earlier mission.