10 Most Disturbing Stargate Moments

In one of the darkest events of Stargate Atlantis, the expedition encounters a Lantean Battlecruiser flying at relativistic speeds. When they come to a rest, the Lanteans struggle to accept the reality of the time that they have landed in. This ends up being a deadly mistake.

The Lanteans return to Atlantis and, arguably justifiably, take the city back. From their point of view, it is their home and the expedition has simply been keeping the place warm for them. They do go about it in a slightly less than friendly way.

The door is left open to future relations and the Atlantis expedition is sent away, bar Richard Woolsey and Jack O'Neill. O'Neill reports an Asuran ship is inbound, but the Lanteans shrug this off. They created the Asurans, and gave them a base command never to harm their creators. They send a ship to greet the Asuran vessel.

Their envoy is destroyed and what follows is a massacre, with all Lantean settlers in the city wiped out in a single stroke. O'Neill and Woolsey survive to tell the tale to the SGC, but one of the last surviving human-form Lantean communities is murdered by the Asurans, and in small part by their arrogance as well.