Mass Effect features some of the most interesting alien races in all of gaming, and they’re one of the main reasons behind the series’ massive success. But the aliens we encounter in-game are just a small fraction of the lifeforms that inhabit ME’s version of the Milky Way.
Enigmatic sentient species like the Yahg or the Leviathans, as well as non-sapient creatures like Harvesters and Thresher Maws, give us an idea of what else might be lurking in the galaxy. There’s also the Thorian, a unique lifeform with incredible mind-controlling powers that’s said to be over 50,000 years old. But perhaps even more interesting than all of those are Mass Effect’s extinct races. Races like the Protheans, Rachni, or Leviathans will not be included on this list since they still have surviving members during Mass Effect Legendary Edition, so they’re technically not quite extinct. Meanwhile, the aforementioned Thorian is believed to have been a one-of-a-kind creature and thus not part of a race. Probably.
8/8 Inusannon
The Inusannon are the only extinct race that actually gets depicted in Mass Effect Legendary Edition. You can find statues of this mysterious species on Illos during Mass Effect 1, and they look pretty creepy, to say the least. Due to the massive amount of Prothean ruins scattered across Illos, it was initially believed that the statues were meant to depict them. However, we learn later on that the Inusannon colonized Illos long before the Protheans discovered it.
According to the Codex, the Inusannon inhabited the galaxy at least 127,000 years before the events of Mass Effect. We also learn that the Inusannon waged war against another extinct race known as the Thoi’han. A series of major battles were fought between the two over the planet Eingana located in the Omega Nebula. Small pieces of debris from their starships may still be found on Eingana, but the planet is too dangerous for exploration. Nothing else is known about either the Inusannon or the Thoi’han.
7/8 Oravores
The Oravores are another extinct species that gets mentioned a couple of times throughout the series, specifically during Mass Effect 3. As with all the races on this list, we don’t know a lot about them, but we do find out that the Oravores lived around the same time as the Protheans and came into conflict with them.
Even more interesting is the fact that the Oravores also came into contact with primitive Asari and even invaded their homeworld of Thessia at one point. If you bring Javik to Thessia during ME3, he mentions how the Protheans intervened and stopped the Oravores from conquering the Asari homeworld. Modern Asari would eventually see the event as a mythological story in which the goddess Athame fought jealous gods to protect their species.
6/8 Densorin
Just like the Oravores, the Densorin were part of the same cycle as the Protheans. There are no records about the two species fighting each other, but we do find out that the Densorin waged war against the Oravores at one point. According to Javik, the Densorin were even more advanced than the Protheans in some ways, being capable of understanding complex topics that eluded his race.
But despite being highly enlightened, the Densorin also had a dark side. When the Reapers invaded them at the end of their cycle, the Densorin tried to appease the machines by sacrificing their own children in the hope of being spared. Needless to say, the Reapers were not moved by the gesture and destroyed them along with all other intelligent life in the galaxy.
5/8 Zha’til
The Zha’til are the previous cycle’s equivalent of the Geth, though their story is a bit different. This race of synthetics was created when a race of organics known as the Zha augmented themselves with advanced AI technology that allowed them to survive on their dying homeworld. Unlike the Geth, the Zha’til AIs didn’t turn on their creators, however, they were subjugated by the Reapers while the Zha were indoctrinated and transformed into Husks.
The Zha’til were kept around as thralls of the Reapers and were placed into mechanical bodies that started to multiply exponentially until they blotted out the sky, according to Javik. In order to stop them from spreading to other planets, the Protheans caused the star of the Zha’til homeworld to go supernova, destroying the system and the entire race with it.
4/8 Arthenn
The Arthenn are an extinct space-faring species that predated the Protheans and even the Innusaon. They are believed to have lived around 300,000 years ago and had a civilization that spread across multiple planets. There is evidence that the Arthenn inhabited multiple worlds across the Zelene system, which is located in the Crescent Nebula at the edge of Asari space. Their technology is believed to have been comparable to that of the present Council species.
The Arthenn are mentioned several times in Mass Effect Legendary Edition where it is theorized that they hailed from the planet Helyme. There is evidence that the planet faced a mass-extinction event that wiped out all lifeforms, though its causes are unknown. Remnants of the Athenni civilization can also be found on Gaelon and Epho, two other planets found in the Zelene system. Based on the impact craters found on Epho and the unusual debris still floating around Gaelon, it seems likely that the Arthenn were wiped out by the Reapers.
3/8 Zeioph
While some extinct species like the Arthenn left behind quite a bit of evidence of their existence, others like the Zeioph vanished without a trace. Well, almost. We know that the Zeioph inhabited the planet Armeni, which is located in the Knossos system, Artemis Tau cluster. The only currently inhabited planet in the system is Thereum, which contains a high number of Prothean ruins.
Unfortunately, it’s impossible to know whether the Protheans lived around the same time as the Zeioph. The only thing we know for certain about the Zeioph is that they built millions of elaborate crypts beneath the surface of Armeni, near the equator. Many human archeologists have expressed an interest in excavating and exploring the crypts, but they have so far been denied by the Council.
2/8 Unidentified Spacefaring Primates
Many of Mass Effect’s extinct races don’t have a name, but they did leave behind traces of their existence. One such example can be found on the planet Bothros in the Hekate system where explorers found evidence of a civilization of space-faring primate-like beings. Interestingly enough, remains of the creatures still wearing space suits were found on the planet along with fragments of their equipment.
Judging by the fact that Bothros is a frozen rock, it’s unlikely that it was the race’s home world. If it was, it must have been transformed by some cataclysmic event given that the primate-like creatures needed special suits to survive on it. Bothros does show signs of orbital bombardment, which must have been caused by a highly advanced species, possibly the Reapers. However, it’s more likely that these creatures hailed from another world and were simply exploring Bothros, but we may never know for sure.
1/8 Unidentified Megacity Builders
Traces of another interesting race without a name can be found on the planet Junthor in the Gagarin system. Here, explorers found remnants of mega structures near the equator believed to have been built by an advanced spacefaring species. Few traces of their civilization remain on the planet aside from ruins and a column bearing a strange inscription.
The inscription apparently baffled linguists for centuries until a group of Asari finally managed to translate it. The inscription reads, “walk among these works, and know our greatness,” which sounds like something Warhammer 40K’s Necrons would say. In addition, the column also had a second inscription that seems to just be a nod to the classic sci-fi movie Forbidden Planet.
