The Leviathan is the quaternary antagonist of Disney's 41st full-length animated feature film, Atlantis: The Lost Empire. While an artificial intelligence designed by the otherwise good people of Atlantis, the Leviathan is homicidal and extreme due to its programming, murdering countless explorers on their search for the lost city.
In The Shepard's Journal, the Leviathan is described as a killer sea monster lurking in the waters around Atlantis.
Atlantis: The Lost Empire
During the prologue of the film, the Leviathan is seen being swallowed up by the tsunami that sunk the city of Atlantis. Some time after this, it was apparently appointed protector of the city. Despite the fact that the people became more open to the idea of visitors over time, the Leviathan was left, perhaps due to being forgotten (as much of the more ancient culture was forgotten over time by the Atlantean people).
Roughly 8,000 years after the sinking of Atlantis, the submarine Ulysses arrives searching for the lost city, carrying the main characters on board. As they pass through the Leviathan's lair, Milo Thatch notes that it contains vessels from almost every era, implying that the Leviathan has killed countless amounts of people who have entered its lair in the past. The Ulysses awakens the Leviathan, which attacks and pursues the submarine. It ensnares the sub in its claws, and Commander Rourke and Helga Sinclair begin commanding a counterattack. They order the launch of the Sub-Pods, which fire torpedoes and cause the Leviathan to drop the Ulysses. However, the Leviathan retaliates by firing an electric bolt that severely damages the submarine. The main cast and a handful of crew manage to escape the Ulysses in escape subs before the Leviathan fires another electric beam and blows up the ship, killing all remaining crew.
It then pursues the escape subs, destroying a few with its claws and electric blasts. However, when the survivors pass through a crevasse, the Leviathan becomes stuck. However, it continues to fire electric blasts, destroying more Sub-Pods before the last of the crew escapes into an underground cave system.
The survivors hold a memorial for the presumably hundreds killed by the Leviathan.
Atlantis: Milo's Return
The Leviathan is presumably fixed by the events of the sequel. It investigates the crew as they enter the secret entrance, but, sensing the crystal necklaces worn by the crew, identified them as allies and allowed them to pass.
It is unknown what became of the Leviathan after Atlantis returned to the surface.
The Leviathan resembles a gargantuan mechanical lobster with two massive claws, two smaller claws, a tail, and several bladed legs. It is dark turquoise in color, emblazoned with ancient Atlantean symbols and patterns. It has large, glowing red eyes and several tentacle-like appendages surrounding its "mouth", which is its electric blaster.
Despite its size and the fact that it is a machine, it has shocking maneuverability and durability, able to easily swim fast enough to catch up to racing subs.
What motivated Leviathan to become an aggressive and murderous mechanical monster is actually not malicious intentions, but rather it's program to defend Atlantis from threats. Unfortunately, when Atlanteans began to forget their once advanced technology as much as they began to open with visitors, they also forgot about their mechanical guardian's existence as well as its programming: With none of the Atlanteans whom keep an eye on Leviathan to aid it differentiate between friendly visitors and hostile ones, it resulting the mechanical monster indiscriminately attacked anyone that approaching Atlantis. This is apparent as during the events of first film, Leviathan indiscriminately attacked and killed most of Ulysses' crew due to no Atlantean whom accompany it.
The only way to help it differentiate between friend and foe is by wearing Atlantean crystals, as those whom possessed the crystals would be perceive as friend.
Sketch of the Leviathan in the Shepard's Journal.
The Leviathan's mechanical eye.
The Leviathan ensanares the Ulysses.
The Leviathan destroys the Ulysses and kills all on still on board.
The Leviathan's red eyes.
The Leviathan destroys another escape sub as the rest escape.
There is mild debate on whether or not the Leviathan counts as a "villain", since it is simply doing as it was programmed to do. However, most consider it as one due to its malicious programming, its role in the film, and its massive body count. Disney also considers it a villain within the context of the film.
The Leviathan, while one of the more underrated and forgotten Disney villains, has one of (if not the) largest body count in any animated Disney movie. It is shown that the Leviathan not only kills the many passengers and crew on the Ulysses, but has sunken and destroyed countless vessels in the past.
In Atlantis: Milo's Return, it is mentioned in passing as a possible suspect regarding Kraken attacks, though the Kraken is revealed later to be another being entirely.
In early development, Milo figures a way to destroy the Leviathan when in a Sub-Pod with Helga Sinclair. However, this concept was dropped early in pre-production.
The Leviathan also appears as a boss in the video game adaptation.