Nexus Zero is an alternate dimension that links to the Shattered Beasts universe.
Nexus Zero is the prision in which the Vok where trpped to stop them from killing more innocents. On the physical plane it is nothing but a swirling mass of energy, which allows the vok whose bodies are pure energy to survive. If one delves deeper, however, you will find that the Vok had managed to trap Sparks in with them. This allows them to feed of of their fear and to derive sick pleasure from the defense Sparks' pain. It is sealed with a Quadrent lock which has held for millons of years, until a transwarp disturbance created a small fissure allowing the Vok to escape.