Mass Effect, Mass Effect 2 & Mass Effect 3
The asari were the first species to discover the Citadel. When the salarians arrived, it was the asari who proposed the establishment of the Citadel Council to maintain peace throughout the galaxy. Since then, the asari have served as the mediators and centrists of the Council.
An all-female race, the asari reproduce through a form of parthenogenesis. Each asari can attune her nervous system to that of another individual of any gender, and of any species, to reproduce. This capability has led to unseemly and inaccurate rumors about asari promiscuity.
Asari can live for over 1000 years, passing through three stages of life. In the Maiden stage, they wander restlessly, seeking new knowledge and experience. When the Matron stage begins, they 'meld' with interesting partners to produce their offspring. This ends when they reach the Matriarch stage, where they assume the roles of leaders and councilors.