Metroid

The Metroid appeared in 1986 video game of the same name, but it did made a cameo appearance in 1997 video game called Kirby's Dream Land 3. Metroids are the titular creatures of the Metroid series. Originating from the planet SR388, they first became known to the universe at large when Space Pirates stole a batch of specimens from a Galactic Federation research vessel and attempted to exploit them as bioweapons. Since then, the species was spread out on numerous planets, endangering all life present due to the Metroids living off on the mysterious "life energy" of their prey.

The Metroids were long rumored to be created by an ancient race, though their motive for doing so remained a mystery to the rest of the universe. Eventually, it came to light that the Chozo were responsible for genetically engineering the species, in order to prevent the spread of the more dangerous X Parasites. Appropriately, the word "Metroid" in the Chozo language roughly translates to "Ultimate Warrior".

The species became extinct in the wild at the end of Super Metroid; all subsequent Metroids in the timeline have been created in laboratories using the DNA of the last and now-deceased Metroid from SR388.