 Because the Cyberman Army and the Void Ship containing the Cult, the Genesis Ark, and the Dalek Army within had travelled through the void, they had all picked up 'void stuff' which, when the Doctor reversed the flow of the radiation, sucked both armies, the Genesis Ark and the Void Ship back into the Void.Dalek Sec and the Cult were able to escape the slaughter by initiating an Emergency Temporal Shift.Along with the rest of the Cult of Skaro, he ended up in New York in 1930 and established a base beneath the Empire State Building.