[quote=@axleonex]
[@TheUnknowable] I'd like to add Portal and Half-life too but I'm never sure which date to put those events in. I also haven't played the games, so I'm a bit unaware what they'll add to the universe.

Assassins creed is vaguely included in the timeline, I think I need to add abstergo/Templars to the miscellaneous factions (or did Mass Effect's Cerberus descend from Abstergo?)
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I just see them as adding depth by describing the tech history of the planet.  I would say that Cerberus is the Templar reborn.  Maybe they are an offshoot.  Maybe John Sheppard or John 117 is a descendant of Desmond or the Lone Wanderer?

I'm also wondering if maybe Halo should predate Mass Effect, as humans don't have energy weapons until the end of Halo (when suddenly the Spartan Laser shows up, working like a mix of the Tesla cannon and laser rifle from Fallout), but have them routinely is Mass Effect.  Also, the portal thing from Halo 3 could be an earlier version of the Mass Relay, and humans find a new one after that one stops working.  It would also explain why cybernetics are so much more advanced in Mass Effect, and everyone has personal shields, unlike in Halo where only the Chief and the Arbiter had them.  Human Tech + Covenant Tech would make a pretty accurate version of the Normandy's tech.