The Baku is an alien of an unknown species that crashed into the Frozen Planet some time in the past, and brainwashed the native Mer aliens who fed on its growths, leading them into worshiping it as the "garden of life". Queen Luxia fell under its control first and soon began sending her people to be eaten as punishment, though all believed they were simply returning to the garden that created them. The mer aliens are freed from the Baku's control when it is defeated by Lance and Hunk.
The Baku is a large brown serpentine creature with a mass of plant-like growths lining its entire spine. When coiled up, the Baku easily passes for a garden. Once uncoiled, it clearly has a white segmented underbelly with a purple fin running down its whole body, and a head that splits into four different jaws lined with sharp canines. It has a large green fin on the tip of its tail and two green pectoral fins close to its neck, almost like a hood, with smaller purple fins tucked underneath. The Baku has no apparent eyes. It has a high-pitched shriek able to be heard clearly underwater.
Consuming the growths from the Baku causes the consumer to fall under the Baku's control, albeit the ability seems passive in that the Baku does not appear capable of actively manipulating another creature by overtaking its body. The ability only makes anyone who eats part of it to become more listless, under an eerie calm, and see the Baku as deity to worship and to eventually return to.
- The Baku's control leads people to believe they are somewhere "safe and warm".
- It is not known where the name "Baku" originates.
- The Baku species has only been seen once, and it is not known if more of it exist.