Vanduul
Vanduul are a sentient, nomadic species of bipedal aliens. Males live on ships and form organized groups called "clans" or "hordes". Vanduul made first contact with Humanity in 2681 in Star Citizen. Since these first encounters, they are usually aggressive towards other races, especially humans. All attempts that Humanity has made to contact them peacefully have failed. After a first big wave of attacks against the human-settled sectors between 2681 and 2712, they constantly raided United Empire of Earth's border territories. Their conflict with the UEE in the Tiber system over the following 250 years lead to millions of dead human soldiers and civilians.
The Attack on Vega II on 2945-10-05 caused the UEE Senate to formally declare an interspecies war against the Vanduul on 2945-11-11 and confront them in the Oberon system in 2946 (Operation Mandrake).