You battle the five-headed Hydra in the "gnarly monster" cave within the underwater realm of Poseidon.
The Hydra will try to strike you by thrusting out one of its heads. When it does, you must be ready to jump before it does, then land on top of the head, knocking it out. Repeat this for all five heads, then swim below to get a scale from the defeated monster. If you take too long, the heads may revive!
(*outside and above the cave is the Giant Pearl, which you also need.) How_do_you_defeat_the_Hydra_on_Mythology_Island
Creatures from Greek Mythology include the Sphinx, the Minotaur, satyrs (usually guards), the Hydra, Cerberus, and Medusa. Non-mythological creatures are the flaming skulls and river monsters on the River Styx.
The hundred-eyed giant Argus Panoptes; when he was killed by Hermes his eyes were put upon the tail of the favored bird of Hera, the peacock.
the river styx
There is a three headed dog in Greek Mythology, that guards he underworld. It is called Cerberus.
Cerberus. be careful when you say hell. what you actually mean is the underworld there was no heaven or hell in greek mythology only mount olympus and the underworld... the underworld was then split into sections that resemble heaven, hell and purgatory.
Ladon the Dragon
Cerberus is the name given to the entity which, in Greek and Roman mythology, is a multi-headed dog which guards the gates of Hades, to prevent those who have crossed the river Styx from ever escaping.
Cerberus, the three headed dog.
Polyphemus was said to live on an hidden island. Percy Jackson says he guards the Fleece, but reality says we don't know if greek myths ever told us that.
with the camo suit
You have to get a balloon.
The monster that guards the exit from the Underworld is Cerberus (Kerberos).