Leviathan

Leviathan is a summon that appears in most games in the series. It is a sea serpent, and its attack, Tidal Wave (also known as Tsunami) deals water-Elemental damage to all opponents. In the Super NES version of Final Fantasy VI, it was replaced with the Esper Bismark. However, it will appear in the Game Boy Advance version of the game.

Final Fantasy III
"White" effect petrifies all targets. "Black" effect causes Wind daamge. Full "Levia" does large amount of Thunder damage?

Final Fantasy IV
Leviathan plays a major role in this game. He is the king of the Summoned Monsters that live on a parallel plane of existance in the Underworld. He knew that Rydia of Mist was one of the last surviving Summoners, and that she was potentially the most powerful. As a result, when Rydia was travelling with Cecil, Edward, and Yang to Baron on a ship, Leviathan attacked the ship and sucked Rydia into the Land of Monsters. He is later obtained as a summon once Cecil and his friends visit him in his home. They must defeat and obtain Asura in order to even talk to Leviathan. After obtaining Asura, Leviathan will challenge the party to a fight. If the party wins, they obtain Leviathan.

Final Fantasy V
Leviathan is a Level 5 Summon that guards Istory Falls. He protects the ancient tablet that lies there, and the party must fight him to get both the tablet and him.

Final Fantasy VI
Leviathan appears in the Game Boy Advance version. He must be defeated by the party.

Leviathan teaches Flood x2.

Final Fantasy VII
The Leviathan Materia is found in Wutai after Yuffie defeats Godo. It casts "Tidal Wave" and costs 78 mp.

Level -- AP Needed
 * Level 1 --     0
 * Level 2   --   18000
 * Level 3  --    38000
 * Level 4    --  870000
 * MASTER  --    100000

Stat Change
 * Magic +1
 * Magic Defense +1
 * Maximum HP -5%
 * Maximum MP +5%

Final Fantasy VIII
The Guardian Force Leviathan can be Drawn from Garden Master NORG.

Final Fantasy IX
The Eidolon Leviathan is obtained automatically at the Iifa Tree. It is taught through the Aquamarine. Only Princess Garnet can summon it.

Final Fantasy XI
Leviathan appears as one of the avatars available to Summoners in Final Fantasy XI. He is one of the 6 prime avatars representing the six elemental forces in the game (aside from light and dark) with Leviathan representing Water.

Final Fantasy Tactics
Leviathan can be learned with 850 Job points.

Etymology
Leviathan is a violent sea creature that is referred to in the Old Testament of the Bible as well as the Talmud and some other ancient Jewish texts. During the golden age of seafaring, the term Leviathan became synonymous with any large sea creature, sometimes describing whales. The Bible only refers to Leviathan in passing, and it has been speculated that it could have represented the sea as a whole, while the Behemoth represented the land, and the Ziz represented the sky. The Talmud and other ancient Jewish sources refer to Leviathan more specifically as a sea serpent, sometimes with multiple heads capable of breathing fire, that was made on the fifth day of Creation. It is said that during the end times, God will make tents, or sukkah, out of the skin of Leviathan for the righteous to live in. Some have speculated that Leviathan was based on a real animal, the most popular theory being the Nile crocodile. To the Ugaritic people, Leviathan was a god of evil. To the japanese, Leviathan was, and is, god of the sea.