The Metarex (メタレックス Metarekkusu?, lit. "Metalex"), is a large army of cyborgs and robots featured in the anime series Sonic X. They are led by Dark Oak and have one motive: to control the galaxy (or so it seems). The Metarex serve as the main antagonists throughout the final season of Sonic X, almost replacing Dr. Eggman, although unlike Eggman, the Metarex had everything laid out in advance so that they could both protect vital operations and attack enemy worlds at the same time. They are also known to be very dangerous and vicious as they will do everything just to destroy all planets in the galaxy even if it means losing part of their army. The Metarex became extinct after Dark Oak's death.
The Metarex is a race of robotic marauders, equipped with highly advanced and powerful weaponry. They have traversed the galaxy, stealing the so-called "Planet Eggs" and objects of great power, leaving whole worlds dead or dying in their wake. Among their victims are Cosmo's home-world, along with every member of her species except her. They also implanted Cosmo with a hidden sensor in her brain, turning her into an unwilling spy.
The Metarex have a plan known as Operation Duplicate. A large part of this plan involves creating several counterfeit Chaos Emeralds, with the power of the originals. These copies, however, seem to phase out after use. This plan also involves using chaos energy to mutate Planet Eggs, growing them to unusual sizes. Their plans also include wiping out non-plant life in the universe, leaving plants to rule. The leaders of the Metarex are, in truth, male members of Cosmo's species. Their robotic-like shells were created by using Planet Egg energy, from their own planet, for the result of a crystallized evolution. Dark Oak and his commanders are the only Metarex who are not entirely mechanical; while their soldiers are automatons, the commanders are simply encased in thick armor.
Ultimately, the Metarex goal is the galaxy's Forestation—the eradication of all life except that of plants. To achieve this, the Metarex need the Planet Eggs and Chaos Emeralds to supply water and light. So nourished, they require the power of an event that occurs once every thousand years in the center of the galaxy on Planet Aqurius. With the energy, the Metarex would be able to wipe out all non-plant life.
Some Metarex are very powerful, too strong for Sonic the Hedgehog and his allies to defeat without assistance from either an ally, some sort of device, or a Ring. There are multiple types, and they appear in every environment. Many Metarex wield a blade weapon of some type and most come equipped with missiles as well. The Metarex became extinct after Dark Oak's death.
- Black Narcissus' Battleship
- Dark Oak's Battle Ship
- Metarex's Mother Ship (appears to have been built by Dr. Eggman).
- Pale Bayleaf's Battleship
- Red Pine's Battleship
- Yellow Zelkova's Battleship
- The word "Meta-" is a prefix that means "change or transformation," or "one level or description higher," and the word "Rex" is a word that means "royal" or "king".
- The Metarex leaders are named after plants or trees. They would eventually be revealed as the male versions of Cosmo's species.