There a rumor in the galaxy about a device that can turn someone into other species of alien races.
This is the omnitrix the most powerful weapon in the universe of level 20.
However the real purpose of the omnitrix isn't to be a weapon it was to keep other species alive like the petrosapian who are extinct and the arburian pelarota who went extinct due to a parasite that killed of the planet.
However other alien saw it as a weapon and wanted it for power.
However among them was vilgax the conqueror of planets and a destroyer.
The creator of the omnitrix send it to the plumbers who were an alien police force in the galaxy.
However during its transfer the cargo ship vilgax tried to get the omnitrix which led to the device being sent through the galaxy away from vilgax.
Which led to the pilot rigging the ship to explode which leg to leave the conquer gravely injured.
To the point that it would take years for his medics to fix his body with some enhancements to prevent something like that again but again it would take time.
After that incident no one heard of the omnitrix ever again and some think it's still around while others say it's just a myth.
The creator of the omnitrix just said good riddance since he rather the device be gone then cause him trouble again.
However unknown to them the omnitrix pod landed on earth in an area filled with garbage.
And it would be there for years until a boy would fall from the sky and wield it at the cost of painting a target on his back not just from enemies from his world. But from others planets