King Metalix is a robot double of Nylus the hedgehog from an alternate universe,where another version of Doctor Eggman destroyed planet Earthius and robotized him and his friends. He leads a powerful orginazation of Metal sonic like robots from all over the Omniverse.
Metallix used to be just like Nylus. Until one day,an alternate counterpart of doctor Eggman entered his world with Chaos Control. This version of Eggman had conquered Mobius and Earth,once he entered this world,he decided to conquer it. Eggman decimated planet Earthius. Nylus and his friends tried to finish the inter dimensional go kart,but failed. Nylus and his friends were captured and robotized. Eggman ruled Earthius for many years. Soon after,Nylus began to become self aware and rebellious, disobeying Eggman's orders. Soon,Nylus eventually rebelled agaisnt Eggman. He ultimately killed Eggman by spreading a virus to all of his robots,they killed Eggman. After that,Nylus decided to form an army with his new loyal robot subjects. He then called himself "King Metallix". He had his new army rebuild Earthius into a new robot world. King Metallix ruled over all. After many centuries of his rule,Metallix decided to create inter dimensional travel,so he could set out to conquer new worlds. Once he created a portal,he went into a dimension with Metal sonic like counterparts of the former inhabitants of planet Earthius. Metallix discovered that there are other robot counterparts in other dimensions and universes. He decided to put this to his advantage,since then he's been recruiting robots from other dimensions and universes into his army.