The last great Cyberwar, (COMIC: Vortex Butterflies) otherwise written as the last Great Cyber War, was a conflict that saw multiple battles fought against the Cybermen. (GAME: The Edge of Reality) The war took place before the Colonial Wars that occurred sometime circa the 30th century. (AUDIO: Bad Day in Tinseltown)
During the war a bloody battle took place on Ryzzenbach, where the fields became filled by human and Cyber-bodies. Legend held that the CyberReaper assembled itself from the Cyber-remains in an act that appeared to be done by sheer will and, despite the Cybermen's lack of emotions, a need for vengeance. (GAME: The Edge of Reality)
In the far future, Gabby Gonzalez noted that "fake Cyberdudes" liked to reenact battles from the last great Cyberwar. (COMIC: Vortex Butterflies)