Ardat-Yakshi

An Ardat-Yakshi (meaning 'Demon Of The Night Winds' in Asari) is a rare condition in Asari, specifically effecting their nervous system. Whilst the condition causes no weakness in the effected Asari's nervous system, during mating the infected Asari's nervous system completely overpowers and dominates that of her mates, causing brian hemorage and then death. The Asari becomes smarter, stronger and more deadlier after each 'mating'. The only known 'sufferer' of the condition is Morinth, the daughter of Samara.

Whilst not known how much the Asari's strength increases after each mating, or whether the matee makes any difference, Morinth's continuous use of the condition over 400 years allowed her to match her mother, Samara, despite 600 years of extra gained experience, to the point where Shepherd had to intervene.

If Shepherd mates with Morinth, he becomes another victim of the condition and suffers a brain hemorage and dies.