Ardat-Yakshi

Ardat-Yakshi (meaning 'Demon Of The Night Winds' in an old asari dialect) is a rare condition in asari, specifically affecting their nervous systems. Whilst the condition causes no weakness in the affected asari's nervous system, during mating the Ardat-Yakshi's nervous system completely overpowers and dominates that of her mates, causing brain hemorrhage and then death. The asari becomes smarter, stronger and deadlier after each 'mating'. There are currently three known asari with this condition, One of them, Morinth, has chosen to embrace her condition.

The condition is impossible to identify until the asari reaches maturity, by which time it is too late to correct. When diagnosed, afflicted asari are given a choice: live in quiet seclusion or be executed. Asari do this because it is an addictive condition; Ardat-Yakshi feel compelled to mate, a compulsion that grows stronger each time they succeed. While it is not known how much the asari's strength increases after each mating, or whether the victim makes any difference, Morinth's continuous use of her condition over centuries allowed her to match Samara's power and experience, despite the 600 year difference between them, to the point where Shepard had to intervene.

Morinth claims that the Ardat-Yakshi are the genetic destiny of the asari; a claim contradicted by the fact that all Ardat-Yakshi are sterile.

If Shepard mates with Morinth, the Commander suffers a brain hemorrhage and dies, becoming another victim of the condition.

It is suspected that this condition is what lies at the root of the asari prejudice against purebloods. Samara, a pureblood herself, states that the condition is as old as the asari species, and that it appears much more frequently in the daughters of purebloods.

Trivia

 * The turian shopkeep at the Zakera Cafe sells asari honey marinades. He says the marinades are created by sufferers of Ardat-Yakshi at a monastery.
 * 'Yakshi' may be a reference to nature spirits found in Southern Asian Mythology. 'Ardat' may be a reference from the Akkadian word Ardat-Lili, in turn associated with the Middle Eastern storm demon Lilith.