|Mass Effect 2|
Mass Effect 3
Ardat-Yakshi ("demon of the night winds") are asari suffering from a genetic disorder preventing conventional melding of nervous systems during mating. Instead, Ardat-Yakshi electro-chemically ravage their partner's nervous systems, in extreme cases leaving victims as vegetative invalids or corpses. Asari psychologists regard this incapacity for mental fusion as preventing the development of empathy, leading to psychopathy. There is no known cure.
The disorder generally begins in infancy, reaching full pathology during Maiden adolescent sexual development. While seductive and sexually-driven as other asari, Ardat-Yakshi are congenitally sterile.
Ancient asari mythology held Ardat-Yakshi as gods of destruction, depicting them as villains of countless legends and as the anti-heroes of numerous asari epics.
Contrary to popular belief, Ardat-Yakshi are neither extremely rare (around one per cent of asari dwell on the AY spectrum), nor are they all murderers. Most cultivate and discard countless exploitative or abusive relationships during their legally marginal lives. Despite rumors of Ardat-Yakshi syndicates, by nature Ardat-Yakshi are incapable of long-term cooperation.
As a disproportionately wealthy species, asari employ their economic reach and media ownership to hide the AY pathology from the galactic community, placing most Ardat-Yakshi in monitored work programs or seclusion. Only the most aggressive cases are sentenced to sanitaria and prisons or to the execution lists of justicars.