The universe of Mass Effect is filled with unique characters, interesting factions, and diverse races that weave an intricate tapestry of emotional and political intrigue. Every person and group has an angle they are playing to accomplish their desired goal, all set in the foreground against the terrifying backdrop of an ancient threat. These complex characters and group are what makes Mass Effect's universe so compelling, perhaps none more so than the Krogan race.
The Krogans are one of the most interesting races in Mass Effect, with a slew of fun characters like Urdnot Wrex and hilarious questlines like helping a couple of Krogans get some sushi. One of the darkest parts of Krogan history, though, is the events of the Krogan War, which has a lasting effect on the worlds and missions Shepard will experience. The Krogan's warrior culture made them one of the most powerful fighting forces in the galaxy as their technology advanced - a trait the Citadel Council was happy to exploit in the Rachni Wars, but once that was over and the Krogans continued to rapidly expand, the Council saw the threat Krogans posed.
Krogans originated from their home world of Tuchanka, an incredibly harsh planet filled with vicious predators and limited resources. To counter this Krogans evolved to procreate rapidly to have enough members of the species survive and develop a strong combat culture akin to their Klingon inspiration. These factors along with their technological prowess made their race a perfect storm for galactic conquest, one which the Citadel Council helped exacerbate by giving them the Rachni planets after the Krogans won the war.
The Krogan Rebellions In Mass Effect
After the Council used the Krogans to defeat the Rachni, they believed the Rachni planets would be enough to satisfy them. They didn't account for the Krogan's rapid growth rate and nature as a species, leading to the next major threat in the galactic system. The Krogans expanded their empire planet by planet to meet the needs of their rapidly growing population, one of a number of Salarian strategic errors throughout Mass Effect's timeline, which eventually led to Krogans attempting to settle the Asari colony of Lisaria. The Citadel sought to intervene, but the Krogans refused to back down and invited open conflict by daring the Citadel to take the planets back.
The Citadel formed the Spectres from top Salarian operatives and Asari huntresses as a strategic task force to use against the Krogan threat, which saw initial success as they were able to destroy energy refineries, cripple planetary networks, and sabotage headquarter space stations. Yet again, though, the Krogan rate of growth proved detrimental as they were able to continually replenish their forces and overwhelm Citadel attacks, proving time and time again why Krogan are such elite fighters. The Citadel then turned to the Turian race for help, with their massive armada and unparalleled military prowess.
The Turians struck strategic blows to Krogan forces from hidden bases they'd established, but this resulted in escalation of horrific proportions as the Krogans then orchestrated asteroid attacks on Turian planets, rendering them completely unlivable. The Turians no longer saw the Krogans as a mission but rather a threat to Turian existence, which led them to seek an end to threat entirely.
Thus the Turians sought help from the Salarians, who, after once helping the Krogans join the Citadel, then proceeded to manufacture the ultimate weapon against them; the Genophage, a powerful bio-weapon that render the Krogans nearly sterile and unable to replenish their species' numbers. While the Salarians intended the Genophage to be a deterrent, the Krogan's are only matched in strategic ruthlessness by Turians, who deployed the weapon.
The Krogans continued to fight as their numbers dwindled, but despite their persistence to battle became futile forcing them to surrender. With heavy losses suffered on both sides and the lasting damage done to Krogan race, the end of the Krogan Wars left a scar on the galaxy and creates powerful narrative that carries throughout the Mass Effect franchise. Some of the most impactful moments in the series are directly tied to this brutal era.