After the live stream, Bungie has published the video in proper, high quality as well.
The developer diary (which is probably going to be turned into a series in no time) starts out with an in medias res approach: we learn that the main villain’s name is Dominus Gaul, and we also hear the reason of his wrongdoing: he wants to get the Traveller’s light with his Red Legion. (If you know Destiny’s lore, you probably know what that is!)
There’s also some gameplay shown from the mission that was played during the reveal event, but there’s not a lot of time to rest: Bungie goes into bullet points to show how Destiny 2 will be different from the first title. (No spoilers: pretty much EVERYTHING is going to change.)
Destiny 2 will launch on PlayStation 4 and Xbox One on September 8, followed by the PC port at an unknown date – the port will be handled by Vicarious Visions, who is currently developing Crash Bandicoot: N.Sane Trilogy.