Leusinia was immediately beset by kett attackers upon arrival at the Heleus Cluster. During one battle, Matriarch Ishara was left alone while holding off an attack. Her bodyguard, Sarissa Theris, stole a data module from the kett containing a map of routes through the Scourge. Ishara began to falter and begged Sarissa to aid her, as required by asari honor and Sarissa's position as bodyguard, but Sarissa refused, knowing that abandoning Ishara will disgrace her but believing the data module could help the Leusinia escape the kett. Ishara was killed as a result and Sarissa became the new asari Pathfinder.
Mass Effect: Andromeda Edit
If Pathfinder Ryder helps Cora Harper locate the asari ark, they encounter Sarissa aboard the Leusinia. When asked about Ishara's fate, Sarissa then lies about her death, claiming she died attempting diplomacy on the kett.
While aiding in restoring power to the Leusinia's main drive, Pathfinder Ryder learns the truth of Sarissa's actions after discovering an audio of Matriarch Ishara's succession log. Ultimately Ryder has the choice of keeping Sarissa's secret, exposing Sarissa but allowing her to remain a Pathfinder, or exposing Sarissa and replacing her with her second, Vederia Damali.