Void was choked out by Gary in S3 Ep7. Now he returned because Void is the only person who can travel through universes without a machine. So later on after he was choked, he used his last bit of energy to teleport to another Void. And those Voids fused together using a matter changer machine, and both stayed alive in the same body, allowing time for Void to train and take back his revenge on Gary which has..... failed, so far....