Nexus until recently was the primary operating system of Dax's ship... The Nexus. After Dax's stumbling into the ULT Nexus felt abandoned since the only organic that he had known spent more time exploring the vastness of the ULT instead of on the ship, as was his usuall practice.

Deciding that there must be something more interesting out there the AI began construction of a humanoid form. In a rather ingenious fassion he used the nano technology inside Dax's lab to do this. The Nexus used a similar design for his Sentient Core as was used in the ship. However this was far more compact being the size of a small ball bering, like at the end of a ball point pen, rather than a marble. The rest of the space was filled with a lightweight liquid that was conductive to bio-electric current. The form was then covered with a synthetic skin which was able to heal itself using the liquid as well. Using nano-conduits throughout his form also contributed to the final light weight of the body.

The body took the form of the only organic The Nexus ever knew... Dax, except without the implants. After his first experience outside the ship he made some clothing and wore it the next time. After experiencing life outside the ship he refused to go back for fear of Dax's disapproval and his own reassimilation to the ship. He enjoyed this new freedom and inteded to keep it. As a label he took the ship's name and tacked on Dax's last name, to in a sence recognize that Dax was his creator.