The universe of Mass Effect Legendary Edition is expansive and thoroughly fleshed out, featuring dozens of planets to explore and a lengthy in-game codex for fans who want to learn more about the world of the franchise. Mass Effect also introduces players to multiple alien races. Some of these species features heavily in prominent story roles, but others receive far less focus throughout the course of the series.
Alien races in Mass Effect can largely be divided into two categories, Citadel races and non-Citadel races. The Citadel races have diplomatic embassies that can be explored in both ME1 and ME3, and tend to make more common appearances on hub worlds. This includes the Asari, Turians, Salarians, Elcor, and Volus, among others. Non-Citadel races have less presence in galactic politics, but may still feature heavily in the series, such as the Krogan or the Quarians.
Many of Shepard's potential crewmates come from alien species. Mass Effect 1's Normandy crew includes a Turian, Krogan, Asari, and Quarian alongside the human staff aboard the ship. ME2 and ME3 introduce new races into the mix, and Shepard can recruit Salarians, Drell and even Protheans. Spending time with these companions and exploring dialogue options allows players to learn more about some of the many aliens in Mass Effect. But not every species can be recruited to join the Normandy, which is one of many reasons why their presence in the series may be limited.
Rare Mass Effect Alien Race: Vorcha
Due to a lack of resources on their homeworld, as well as the competitive nature of their society, the Vorcha are considered to still be a primitive race by other species across the galaxy. As a non-spacefaring race, they primarily only make it off-world by either becoming stowaways or mercenaries. They can be encountered across Omega in Mass Effect 2, and are a frequent enemy in Shepard's missions there. Their short lifespans, violent nature and lack of formal government and military doesn't grant them much presence in the galactic community. Within Mass Effect Legendary Edition, players will primarily only interact with Vorcha as cannon fodder.
Rare Mass Effect Alien Race: Drell
Drell are a nearly-extinct species, with only a couple hundred thousand individuals present throughout the galaxy. Shepard has the chance to recruit a Drell crewmate, Thane Krios, in Mass Effect 2, and through him is able to learn more about his race. The arid Drell homeworld of Rakhana descended into lifelessness after the onset of industrial expansion. The Hanar rescued a small number of Drell by relocating them to Kahje - where long-term exposure to the humid environment results in lung deterioration, the leading cause of death among the Drell. These various factors contribute to their scarcity in Mass Effect Legendary Edition.
Rare Mass Effect Alien Race: Leviathans
The Leviathans are the creators of the Reapers, forced into hiding to preserve their species from their own synthetic creations. Physically, they strongly resemble the Reapers, as their genetic material was used to create Harbinger - and they possess similar capabilities that allow them to enthrall other species. Through this method, they were able to erase most evidence of their existence over time. In Mass Effect 3's Leviathan DLC, Shepard is able to encounter some remaining members of the Leviathan race and can enlist their help in the war against the Reapers. As Mass Effect Legendary Edition includes almost all DLC from the series, players will be able to play through the Leviathan questline as they progress through the trilogy.