The Icarii, a species closely related to Humans, originated on the planet Vestar. They met their end during the infamous Icarii campaign, a genocidal operation carried out by the Galactic Empire's Lightning Battalion. This battalion, led by General Nim and Colonel Abal Karda, deployed a devastating biological weapon to exterminate the Icarii following months of intense conflict. Only a single member of the Icarii race managed to survive, but was ultimately killed by Darth Vader.
The Galactic Empire referred to the Icarii using the pejorative term Ikies. The Icarii possessed an unusual physiology which allowed them to endure dismemberment, even surviving decapitation. However, splitting the brain in two would kill them. This resilience gave rise to the saying that an Icarii had to be killed seven times to ensure their demise.