Chronologically,
Metroid II: Return of Samus takes place sixth in the
Metroid fictional universe. In the previous Metroid, bounty hunter Samus Aran ruined the Space Pirates' plans to use the newly discovered lifeform known as Metroid. To ensure that the Space Pirates can never obtain any more Metroids, the Galactic Federation sends several teams to the Metroids' home planet, SR388, to destroy them once and for all. However, when none of the teams survive, the Galactic Federation contracts Samus to finish the mission.
This is an example of the ending screen you need to submit on for Mastering credit. You may submit on any screen that comes after this one:
Master Metroid 2 for 24 Game Club points.
Play
Metroid 2 Return Of Samus »
Game Boy and select ArcadeOX Score Mode to receive credit for mastering this game.