Phazon is a fictional substance that serves as a key plot element of the Metroid Prime trilogy. Exposure to phazon is very dangerous, as it can cause dramatic physical mutations and/or mental instability in those it infects. In Metroid Prime, Samus Aran discovers that the Chozo civilization on Tallon IV was destroyed when a phazon meteor struck the planet and corrupted it. In Metroid Prime 2: Echoes, Samus discovers that phazon split the planet Aether into light and dark dimensions and nearly destroyed the Luminoth civilization. In Metroid Prime 3: Corruption, Samus finally discovers the source of phazon, a living planet known as Phaaze, and eliminates it once and for all. With the destruction of Phaaze, all phazon in existence also ceases to exist.
The Space Pirates conducted experiments with phazon, hoping to use it as a source of power or as a weapon. Their experimentation led to the mutation of numerous subjects, including the titular Metroid Prime. After the defeat of Prime at the hands of Samus, the remains of the creature bonded to Samus's Phazon Suit and was reborn as Dark Samus.