A little Metroid II info. Samus destroyed all the metroids on their native planet SR388, including the queen. Right after She killed the queen, an egg hatched and the baby metroid imprinted on Samus. In the Events prior the Fusion, Samus is attacked by parasitic organism known as X. It turns out that metroids kept X in check, and with out them it took over the planet. Much of her Power Suit had to be surgically removed, but the organic components could not be removed as they became a part of her body. To stop X from fully infecting her scientists injected her with gene treatments, modifying her DNA with that of the baby's.