Akuze

Akuze is a human colony on the outskirts of Systems Alliance space. In 2177, Akuze was in the early stages of colonization when all contact was lost with the pioneer team. An Alliance Marine unit was then sent in to investigate, but found only the intact settlement and no survivors. When the unit camped for the night, they were set upon by thresher maws. Not knowing what they faced, the unit was slaughtered almost to the last man; fifty marines were lost, and only one made it back to the landing zone alive.

Mass Effect

If Commander Shepard has the Sole Survivor background, the Commander was the only known Marine to make it out of Akuze alive. If Shepard meets Officer Eddie Lang on the Citadel with this background, Lang will comment on a monument at Akuze and an entire section dedicated to Commander Shepard, suggesting that the colony of Akuze survived the thresher maw massacre, or at least that a new one was established in its place.

Shepard can later discover that there was another survivor, Corporal Toombs, who claims the slaughter at Akuze was not an accident. According to Toombs, the renegade black ops group Cerberus deliberately set the thresher maws on the marines, to study the creatures and see how the unit reacted.

Mass Effect 2

If Commander Shepard has the Sole Survivor background, there is a news announcement about a Shepard Memorial being erected on Akuze, and that once the site is cleared of thresher maws, a commemoration ceremony hosted by Admiral Steven Hackett will be held in 2186.

If Shepard rescued Toombs in Mass Effect, the Commander will receive a threatening message from him about Shepard's new alliance with Cerberus.

Mass Effect 3

If Shepard has the Sole Survivor background, a recording can be found on Cronos Station showing a Cerberus scientist remarking to the Illusive Man that Cerberus caused the Akuze incident, confirming Corporal Toombs' original claims.