Omega-1 Nanite

The Omega-1 Nanite, also known as the Control Nanite, is a large, silver nanite that was injected into Rex by Dr. Rylander. This nanite controls the active nanites within Rex's body and is responsible for the creation of Rex's new machines.

Before the Nanite Event
The Omega-1 Nanite was created during the Nanite Project by the project scientists as a successor to the failed Alpha nanite. Whereas Alpha was designed as a machine-to-machine interface to control the nanites created during the project, the Omega-1 Nanite was designed to work as a human-to-machine interface. Prior to the Nanite Event, Dr. Gabriel Rylander was given the nanite for safekeeping and eventually brought it to his laboratory.

Dark Passage
Gabriel Rylander injected the Omega-1 Nanite into Rex's body. When Rex asked Rylander what he had injected him with, Dr. Rylander replied that he had injected him with "everything".[1] Van Kleiss appeared to be after the Omega-1 Nanite, presumably for its self-replicating program.

The Swarm
When Rex almost drowned in a river, the Omega-1 Nanite restarted his heart, implying that it might help his body when he is in grave danger.[2]

Payback
After Rex was drained of nanites, Dr. Holiday ran an MRI on him and discovered the Omega-1. After activating it using the supply of nanites Rex had previously offloaded at the Purgatory base, Rex regained his original powers plus the Blast Caster.[3]

Alliance
Circe revealed to Rex that Van Kleiss, despite having Rex's nanites at his disposal, was still after Rex. Circe also revealed that she had heard Van Kleiss say that Rex had something that was "the key to everything".[4]

Mixed Signals
Caesar Salazar tried to locate the Omega-1 by downloading a transmitter schematic to the Omega-1. By tracing its signals he discovered his younger brother. His first priority was to find Gabriel Rylander and see to it the Omega-1 was safe. He also revealed that Rylander was in charge of looking after the Omega-1 Nanite before the Nanite Event.[5]

Written in Sand
Van Kleiss later revealed to Rex that the Omega-1 Nanite has a self-replicating program which allows it to create new nanites if necessary.[6] This particular function is later seen when Rex battled Quarry in Hong Kong. The Omega-1 Nanite constantly supplied Rex with more and more active nanites every time they were disintegrated within his system.[7] It also seemed to act on its own accord whenever Rex's life was endangered, summoning the right kinds of new machines depending on the situation.

Heroes United
It is revealed that the Omega-1 Nanite was created to replace the Alpha nanite after it went rogue. Alpha later absorbed the Omega-1 Nanite in order to create an unlimited supply of nanites to sustain itself, which would have destroyed the planet in the process. After Rex was able to compress Alpha into a baseball-sized sphere of nanites, Caesar was able to extract the Omega-1 and give it back to Rex by re-injecting the special nanite.

Endgame, Part 1 and 2
The Omega-1 created a new, full E.V.O form for Rex as he recovered from a great deal of damage in his fight against the Consortium.