Okeanos's Guardian

Okeanos's Guardian is a gotequely-deformed creature, assumed to be a monstrous Goblin Shark, that pursues the player in Endless Ocean: Adventures of the Deep. It lives in an area known as the Cavern of the Gods, a set of ruins that resemble a temple, and attempts to attack the player and trap them inside when they first enter the ruins, and after that whenever they encroach upon its territory.

Appearance
This monstrous beast is a marine creature that most closely resembles a Goblin Shark, though its head and face are much larger than a member of that species normally is (as well as just being much larger overall). It is of a sickly grayish-pink colour and has long, somewhat-wavy fins, as well as an odd extra flap of skin below its jaws, and its teeth are arranged crookedly in a set of strange, almost humanoid-looking jaws. It has a horn-like or nose-like protrusion on its face that is much larger than it should be, assuming that Okeanos's Guardian is simply a mutant Goblin Shark.

Mannerisms
Okeanos's Guardian is a notoriously aggressive creature, going out of its way to drive out anyone who attempts to enter the Cavern of the Gods, the ruins in which it makes its home. The Guardian is, according to the game's lore, a Goblin Shark selectively bred by the Okeanides. The Okeanides were an ancient race of people that were closely intertwined with the sea and its life, and they bred the Guardian in order to protect an unknown something (possibly their treasure, which is the main focus of the game's storyline and perhaps why this creature drives anyone out of its home, which is where the treasure is located). It seems to have a following of normal Goblin Sharks (that also life in the temple) that also attack the player character, and whether they under the Guardian's influence or their own is unknown, but it seems to be that the Guardian is communicating with them somehow, as Goblin Sharks are not aggressive by nature.

It is a creature that is hardly affected by the Pulsar, a device in the game that heals and calms down sick or aggressive sea life, and it shares this characteristic with another gigantic shark, named Thanatos.

Trivia

 * In the game's lore regarding this creature, it is said to resemble Ammit, an ancient Egyptian deity that had the head of a crocodile and the body of a lion, who personified divine retribution.
 * In ancient Greek, Okeanos was the name of the Titan that personified the ocean, meaning that this creature's name roughly translates to "Ocean's Guardian".