Rachni Wars

In the period of around 0 CE, an expedition come across a dormant Mass Relay. This Relay opened a route to the Rachni, a species of highly intelligent hive-minded insects. The Rachni were alarmingly powerful, having massive strength in their numbers. This period of time saw the Citadel Council species fight a losing war against the Rachni forces. This was until the Salarians, who "culturally uplifted" the Krogan from their volatile homeworld(which was caused by a nuclear winter, started by the Krogan), by giving them advanced technology and relocating them to a planet not cursed with lethal levels of radiation, toxins or deadly predators. The true purpose soon emerged as to the turn of fortune for the Krogan by the Salarians as they were needed in the Rachni Wars, to fight the Rachni. This came to great effect as the Krogan rapidly bred. They had the numbers to not only drive the advancing Rachni back, but the ability to endure the harsh conditions of the Rachni] worlds. They were able to pursue them to their home worlds, find the [[Rachni queens, and eradicate the entire species.