Phazon

Phazon is an element in the Metroid series that first debuted in Metroid Prime. It is a substance that was first found by the Space Pirates that seems to make any living beings more powerful and mutagenic. So far, it has only appeared in the Prime series of Metroid games, and will probably stay that way seeing that every known bit of it was deleted in the final game in the series - Metroid Prime 3: Corruption for the Wii.

However, despite this, it's also a very dangerous and potentially fatal element. It is well known that it's killed many civilizations and have also corrupted the four bounty hunters Rundas, Ghor, Gandrayda, and of course Samus Aran. The former three all went mad and attempted to murder Samus, who ended up being victorious in the fight, but was also forced to kill them all.

Whomever becomes infected with phazon is able to put on the PED suit, made by the Galactic Federation (who stole the plans of it from the Space Pirates) which help them utilize their new found ability better than before.