The Phazon came from a meteoroid. The reason it didn't corrupt the entire planet (like in MP3) is because the Chozo were able to seal it off and halt its spread.
Yes, and because the Leviathan (A phazon seed that was sent to the planet to create a Phaaze clone) was sealed within the Impact Crater by the Chozo, a Metroid from inside siphoned the dark energy from it. This prematurely developed it into Metroid Prime: A special case, thus earning its form on the evolution chart.
"You've met with a terrible fate, haven't you."
Gibby, you never tried Zelda? That's definitely a problem; I say to start on one right away. My personal favorites would have to be MM, WW, and LttP. Mostly Majora's Mask, because I felt that the game strayed away from the average formula of traditional Zelda games and gave it a dark feeling, a feeling of dread and anxiety. I rarely feel fear of this magnitude in a Zelda game, so I was naturally drawn to it, and I have to say that my choice to play it couldn't have been better made.
To keep this thread semi-relevant, I have started to play League of Legends, and so far, it's extremely satisfying (albeit competitive).