New Mass Effect Teaser Trailer

It's interesting when you said at the beginning that when we hear the first dialogue someone was watching them. But it seems like all of this we hear goes in chronological order, basically recap the history of mass effect and what we already know. The first one could be when the reapers were watching the mw. The blue thing when we go through the mw, looks like a widow nebula
www.nasa.gov/sites/default/files/styles/full_width_feature/public/images/161746main_image_feature_687_ys_full.jpg
The thing liara walks is a reaper, aside from the one we see on the background. The middle figure is ryder (glass helmet, collar). Gamble hinted we might know who is it if we can find it out. The salarian is kallo and probably drack.
m.imgur.com/ob2LS0S
As for the concept arts, the first one with the big structure seems like jardaan and prothean technology. Probably after they left Andromeda, they traveled to mw thousands of years ago and met the protheans. Gamble hinted it might be both. The other one with the relay could be from the mw. The misty one looks like they explore something. One of the figures looked geth, but don't know if it's just a placeholder thing, we'll see. The one with the Mudskipper, has two figures from the ot (thane, mordin) but i think they're just placeholders. The one's at the right though, it looks like an angara, some say the legs are straight though but it's a rough artwork, the other looks human.