Metroid Bosses.
The Parasite Queen is a Parasite genetically enhanced by Phazon. The Parasites were some of the first species to be experimented on with Phazon by the Space Pirates. Common results were an enormous increase in mass and length, as well as an enhancement of the acidic glands located near the creatures' mouths (the Parasite Queen is seen constantly drooling a green liquid substance).
