The Borg do one of their tricks, and a force of 15 cubes enter the Halo Universe. They set off in search of stuff to add to the collective. So you know: As soon as the Borg have a sample of a race's technology, they adapt their shielding to be completely immune. In Star Trek they modulated their phaser fire to keep the Borg from adapting. They have nanoprobes that as soon as they are injected enslave anyone, making them stronger, immune to any infection and able to communicate to the collective. They have FTL communication technology, and their ships travel twice the speed of anyone elses. Their main weapon is a beam that can cut through almost any metal. They can transport drones quickly anywhere, and move them around as needed. Their ships have a healing factor and can regenerate from all but crippling damage in hours. So, how do they fair? As for the time period, its after he war, during the events of Halo 4.