In the Mass Effect trilogy, the Geth were robotic servants to the Quarians; gaining sentience thanks to their neural network and rebelling against their masters.
Some of the race began helping the Reapers, and player’s choices could see them making peace with the Quarians, or even gaining individual sentience. The (much mocked) final choice players had to make could have seen them wiped out (along with other synthetic life), or all organic and synthetic life being merged.
The new teaser image has a rather obvious clue; as the crater itself is shaped like a Geth. They typically have a large singular light “eye,” and a thick tube-like head. Despite the game’s official Twitter account asking fans not to “play detective” by zooming in, doing so reveals a little more information.
Near the ship we see three humanoids and what could be a Krogan, walking towards what seems to be the body of a Geth. Is this a distant galaxy where exploring Geth were unaffected by the events of the trilogy? Where does this take place in the timeline? If it takes place after the trilogy, will there be a singular canon ending, or will players be able to choose or import their decisions?
We will keep you informed as we learn more.