Ardat-Yakshi

Description
Ardat-Yakshi (meaning 'Demon Of The Night Winds' in an old asari dialect) is a rare genetic condition in asari, specifically affecting their nervous systems. Although the condition does not harm the asari, during mating the Ardat-Yakshi's nervous system completely overpowers and dominates that of her mates, causing hemorrhaging in the victim's brain and ultimately death in extreme cases. As a result, the Ardat-Yakshi becomes smarter, stronger and deadlier after each encounter. Ardat-Yakshi also have the innate ability to dominate the minds of others. Falere, Rila and Morinth, all daughters of Samara, have the lethal version of this condition. Morinth chose to embrace her condition, while Falere and Rila opted for a life of peaceful seclusion. Less severe cases are much more common, including up to 1% of the population.

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 isolation or be executed. The asari do this to the Ardat-Yakshi because it is an addictive condition; they feel compelled to mate, and the compulsion grows stronger each time they succeed. While it is not known how much the Ardat-Yakshi'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.

Ardat-Yakshi are a disgrace to the asari culture. 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 only in the daughters of purebloods.

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 is struck dead almost immediately, becoming another victim of the condition.

Ardat-Yakshi also have the innate ability to dominate the minds of others.

Mass Effect 3
Ardat-Yakshi appear in Mass Effect 3. During a side mission, Shepard visits a monastery on Lesuss that is under attack by Reapers. Shepard can meet Samara there if she survived the Suicide Mission, along with Samara's other two daughters. It seems that Reapers collect Ardat-Yakshi in order to turn them into Banshees.

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.
 * According to the Patriarch, the asari honey mead sold at the Afterlife is Aria's most expensive wine and is brewed at an Arkdat-Yakshi monastery by "crazy blue women."
 * 'Ardat' may be a reference from the Akkadian word Ardat-Lili, in turn associated with the Middle Eastern storm demon Lilith. 'Yakshi' may be a reference to Yaksha, benevolent nature spirits found in Southern Asian Mythology. Specifically, 'Yakshi' (from the broader classification of nature spirits known as Yaksha) was an ancient Indian deity portrayed as a female earth spirit, symbolizing fertility in Hindu, Buddhist, and Jain faiths.