Tetrax is a battle-hardened bounty hunter with a strong desire to do what is right. This is partly due to his involvement in the destruction of his home planet, Petropia.
Tetrax claims that he used to be a being who cared about no one but himself and that is what led him to become a mercenary. It was only after Vilgax destroyed Petropia that he realized the effect his actions had on his own people. That experience made Tetrax into the heroic Omnitrix guardian he became.
Upon first discovering that Ben has the Omnitrix, he laments the fact that out of the planet's six billion inhabitants, the Omnitrix ended up on the wrist of a child. He also berates Ben's lack of strategy in regards to its use. After helping Ben to defeat the other hunters, during which Ben learns to use the Omnitrix strategically, he decides that the Omnitrix is in good hands, allowing it to remain with Ben.
Tetrax helps Ben become a better hero, teaching him to use the Omnitrix wisely (Ben later repays him by reviving the people of Petropia).
Tetrax deeply despises Vilgax due to their history.
As a being who cared about no one but himself, Tetrax became a mercenary and ended up hiring himself to Vilgax. When he finished the job Vilgax gave him, Vilgax created a weapon (using the crystal Tetrax stole) and used it to destroy Tetrax's home planet, Petropia, when his people would not bow down to him. This caused Tetrax to betray his former employer, and he now works as the Omnitrix Guardian and to rid the galaxy of evil.
Tetrax returns in Ben 10: Secret of the Omnitrix. Tetrax arrives on Earth after receiving the Omnitrix's SDM (Self Destruct Mode) signal, and takes Ben aboard his ship in search of Azmuth, the creator of the Omnitrix and the only one who can deactivate the self-destruct function. Unfortunately, Tetrax's problems are multiplied when Gwen stows away aboard his ship, and Ben's transformations are revealed to accelerate the countdown.
On Incarcecon, Tetrax runs into Sixsix, another of the bounty hunters hired by Vilgax who ended up on Incarecon. After a brief battle, he and the Tennysons find Myaxx, Azmuth's former assistant. Because of her, Tetrax is forced to reveal that the Omnitrix's explosion will create an energy ripple that will destroy the entire universe. Tetrax then leads the group to Azmuth's compound on Xenon, where he faces Sixsix again before defeating him by delivering a punch to the face.
Tetrax returns in The Secret of Chromastone, when he comes to Earth demanding that Ben hand over Chromastone. He forces Ben to transform into Diamondhead, thinking he'd transform into Chromastone. He then uses a sonic device to shatter Diamondhead, seemingly releasing Chromastone from the Omnitrix and leaving Diamondhead alive in pieces (literally).
Tetrax gives Chromastone a crystal which he absorbs, then flies off into space. Kevin restores Ben to normal, who then demands an explanation from Tetrax. Tetrax reveals that Chromastone is the only one who can restore Petropia and her people back to life. He explains that the crystal he stole and gave to Vilgax (who used it to power the weapon that destroyed Petropia) was in fact a crystallized back-up for both his planet and its people.
Upon discovering this, Tetrax stole the crystal back from Vilgax and gave it to the freed Chromastone so it could use the crystal to restore Petropia. This was Tetrax's way of atonement for his part in Petropia's destruction. However, his theft of the crystal didn't go unnoticed by Vilgax, who followed Tetrax to Earth, demanding he hand over the crystal.
Tetrax, Ben, Kevin, and Gwen are then chased by Vilgax, who he believes are in possession of the crystal. Vilgax eventually manages to catch Tetrax, demanding he hand over the crystal, but Kevin accidentally reveals the crystal's location. Vilgax flies off to Chromastone's location to discover the newly restored Petropia (Ben and company race to stop him aboard Tetrax's ship).
Angered that someone would use "his crystal" to restore a dead world, Vilgax beats Chromastone, who pleads for mercy, only to find Vilgax has none to give. Tetrax, Ben, Kevin, and Gwen arrive to see Vilgax beating Chromastone. Tetrax attacks Vilgax, but Vilgax's shield protects him from the crystal projectiles.
To Tetrax's horror, Vilgax removes the crystal from Chromastone (before he can revive the planet's people). However, Vilgax discovers the crystal power is gone (thus it is no longer useful to him) and flies off in disappointment, leaving behind the dying Sugilite. All hope seems lost, but the dying Sugilite generates a new backup crystal and hands it to Ben before fading away.
Unsure of how to use the crystal, Ben transforms into Diamondhead (who instinctively knows how to use it). Diamondhead uses the crystal to restore the Petrosapiens to life. Tetrax and a revived Chromastone (who is revealed to be Sugilite) thanks Ben for his help. Tetrax decides to give Ben and company a ride home. Before leaving, Tetrax says he plans on settling the score with Vilgax (aware that both Petropia and the universe won't be safe unless Vilgax is stopped for good).
Powers and Abilities
Being a Petrosapien, Tetrax's body is made of organic, nearly indestructible diamond-like crystals that can refract light, causing him to be immune to most energy weapons.
Tetrax has a limited ability to regrow lost limbs, as well as alter his own physical constitution, making him able to do things such as fire crystal fragment as projectiles, turn his hands into blades, create structures out of his crystals, etc. He's shown to be much more skilled with his powers than Diamondhead.
In addition to his natural powers, Tetrax is an experienced bounty hunter with excellent fighting and strategy skills. Tetrax is also shown to be highly knowledgeable in regards to various advanced technologies, including a great understand of how the Omnitrix works.
In Ben 10: Destroy All Aliens, Tetrax was able to reprogram the Omnitrix.
Tetrax has nearly impenetrable gray armor, a black helmet with a small, green triangle on it, and carries a large rifle. His armor also comes with a retractable helmet and retractable gloves. Tetrax's Petrosapien physiology can manifest through the armor, allowing him to use his powers without removing it.
Tetrax is equipped with various devices and weapons at his disposal, such as a hoverboard, his own personal ship and a sonic device. In the original series, he had a holstered side arm that fired a blue energy beam.
Ben 10: Alien Force
- The Secret of Chromastone (first re-appearance)
- Tetrax had a green hoverboard that he gave to Ben. He also has several others; his favorite was a blue hoverboard which was destroyed by a Tetramand prisoner in Ben 10: Secret of the Omnitrix.
- Tetrax appears in FusionFall. He is found in Forsaken Valley and his Fusion gives out the Humungousaur Nano.
- Tetrax does not appear to have four spikes on his back like Diamondhead, although he had them in a flashback of him when he was young.
- Tetrax's 4" figure was originally called Petrosapien Bounty Hunter when released, while his Transforming Alien Rock figure was called "Hoverboard". He was later properly named in a 3 pack, and Destroy All Aliens packaging.
- Tetrax was the first alien shown in the series to be the same species as an Omnitrix alien.