In 177 BG she accompanied Serena while in the City of Introspection when she was alone with her mother. However one of the Seraphim suddenly attempted to assassinate her (actually put by Iblis Ginjo) but Niriem stopped and killed her. Serena then appointed Niriem the Chief Seraph and showed most confidence to her.
In the following years, Niriem followed closely Serena everywhere, and accompanied her in all her travels, even to the remote Hessra. She even followed her as a representative of the League of Nobles to Corrin.
Serena accompanied by Niriem and other 4 Seraphim, they 'met' Omnius in the Central Spire and apart from the truce, she demanded that Omnius release free all the human slaves. Serena remained imprisoned for some time when Omnius decided to execute her.
Erasmus however realized that Serena intended to become a martyr and ordered the executor robots to stop. Niriem then, following the 'plan B' ordered by Ginjo, delivered a fatal blow, killing her and restarting outrage among the League. The Seraphim launched themselves against the robots in a final stand, and destroyed 26 machines before slaughtered all.