Asari

A relatively new alien species introduced in the Mass effect Universe, Asari are a beautiful (by just about all alien standards in the games) mono-gendered race of humanoids with skin tones in widely varying shades of blue and faces with ridges that resembles a starfish or squid. In both games, the main character (Commander Shepard) has recuited asari for his teams (the first being Liara T'soni, the next being either Samara or her daughter Morinth).

Asari Physiology
Asari are very long-lived women, capable of living up to a thousand years or more throughout the three stages of the lives and possessing by the end of it a great store of experience and wisdom that all asari (and most races) respect. Though not actually referenced how, most asari are very good biotics, possessing skill and power that most races can't come close to without intense training and biotic amp implants. In fact, one of the conditions for an asari to become one of the legendary commandos is to possess biotics from a young age (note that this is relative to them, as they considered Liara to be little more than a child despite being 106 years old).

Asari reproduce from a form of parthenogenesis, as their control over biotics, and thus their own body, melds and syncronizes their nervous system and mind with the "father" partner to explore their genetic heritage and randomize the genes their daughters will recieve. This unique form of reproduction allows the asari to "mate" with just about any species including the Krogan, Turians, Salarians, humans and possibly even volus and quarians. They primarily do this with other species as to "bring about understanding..." of the other races, believing that through this the asari species grows and learns more of their ally and friend species. However, asari can reproduce with another member of their race, but to do so is considered akin to a taboo. Asari believe that "pureblood" asari do not contribute to their race and thus the word pureblood is considered a grave insult.

Though arguably one of the most humanoid races in Mass Effect, a bachelor party on Illium in Mass effect 2 reveals that humans, salarians and even turians believe that asari resemble their race, with the human member of the party humorously asking, "Do you think, you know, the Asari is like controlling our minds?"

Asari, being long lived as they are, have three very different life stages, akin to humans except altered to their long lifespans. First is the Maiden stage, which could possibly be considered to be their "teenage" years (or centuries in their case). During this stage young asari girls have an almost insatible thirst for adventure and danger, many taking up a profession as pirates, mercenaries and dancers *ahem*...

History
According to in game canon refrences, the Asari were the first modern species to discover The Citadel and use of the Mass Relays spread across the Milky Way. They were also the first to suggest a cooperative government between the race of the Turians, Salarians and Asari to regulate commerce and inter-species politics that might well lead to war or tension. In politics, and in some outside cases, Asari play a neutral ground in conflicts and debates, trying to promote peace and cooperation between two or more factions, though young asari maidens are usually very brash and reckless and rarely do this.