Fission Metroid

Fission Metroids are a sub-species of Metroids found only in the Impact Crater on Tallon IV. Due to the extreme phazon radiation the Fission Metroid is invulnerable to all but the beam that matches the color of the metroid. Once shot with the appropriate beam, the Fission Metroid splits in two. During the final battle with Metroid Prime, they spawn from Phazon pools.