Phazon is a biological weapon. I don't think that it is a coincidence that the planets it hit were the strongholds of some of the most powerful races in the galaxy. I think it was fired at them on purpose. And, from the Luminoth Lore entry "Origins", we know that there are at least two more such species, the N'kren and the Vlla. I think it is reasonable to expect that their worlds have also been attacked by Phazon, or will be in the near future. That's two more games right there, with a final one to journey to the planet that is the source of Phazon.Originally Posted by Kawaii Ryűkishi
Also, I think that a Phazon meteor may have struck SR388 at some point. This is due to my observations of Metroid Prime and Dark Samus. Both of those creatures were pure Phazon entities in their final form, and both seemed to be tied to the Phazon that was infecting the world. Metroid Prime was the source of Phazon on Talon IV, and Dark Samus seemed to control most of the Phazon on Aether by the end of the game. I think that the Phazon entity is a chameleonic warrior. It first struck SR388, but was defeated by the Metroids (which were genetically engineered by the Chozo to defeat a different threat, the X virus, as we learned in Fusion). It then absorbed the genetic information of Metroids, and took on the form of the Worm, Metroid Prime. This entity was defeated by Samus, and it then absorbed her genetic material and became Dark Samus. It attempts to become stronger and stronger by absorbing whatever defeated it. Since Samus has defeated it twice, it's form is still that of Dark Samus, as we saw at the end of Echoes.