Odin

Odin is a summoned monster from the Final Fantasy series of role-playing games. Not to be confused with the actual Norse God, his only role in these games is to inflict extraordinary death and destruction upon the enemies he is summoned to attack. He has appeared in every Final Fantasy game from Final Fantasy III through Final Fantasy IX, as well as Final Fantasy Tactics.

Biography
Very little, if any, is known about Odin and his horse. In a majority of the games, he was an extremely powerful summoned creature that, appearing from thin air, would cut a line through all enemies on the screen, splitting them in half, ending their life on the spot. To gain the ability to summon him generally was permitted to a select few (called summoners or callers, to name a couple). On occasion, you had to fight and defeat him in order to gain his power.

His basic physical characterists are that of a demonic-looking knight with horns, a long, curved scimitar as his weapon, and a cape. This progressed to also include a lance-type weapon called Gungnir. He always is seen on his horse, who takes on demonic-type attributes as well, including red eyes, and having body armor. Sleipnir, Odin's steed in Norse mythology, has eight legs; in later parts of the game series, Odin's steed has six legs.

Final Fantasy III
Can be summoned by both Conjurer and Summoner job classes.

Final Fantasy IV
The King of Baron takes the role of Odin in this game. He can be found in the basement of Baron Castle after a specific event in the storyline. After defeating him (only possible after generally gaining notable strength or through Kain Highwind and his Jump ability), he can be called by Rydia. There's a 50% chance he'll follow through with the attack, however, and doesn't work against bosses.

Final Fantasy V
The Summoner job class has ability to call him.

Final Fantasy VI
The Odin magicite can be found from Ancient Castle in the World of Ruin. Odin was apparently the guardian of the castle during the War of the Magi, 1,000 years before the events of the game. Once the Magicite is equipped by any character, they can summon the Odin esper. The instant-kill attack is called Atom Edge. The character can also learn Meteor spell from this magicite. He can be upgraded into the esper Raiden, who has a similar attack called True Edge and teaches the Quick spell.

Final Fantasy VII
Odin materia is found from the Shinra Mansion in Nibelheim. It can then be assigned on weapon or armor, and used in combat.

Normal monsters get slashed in half as Odin rides by (attack name Steel Bladed Sword). If the monster is immune to instant death attacks (most bosses and tougher enemies), Odin throws Gungnir to heavens and it impales the enemy (attack name mistranslated as Gunge Lance). This attack deals non-elemental damage.

Final Fantasy VIII
Appears as a non-controllable Guardian Force; he may pre-emptively strike the enemies at the beginning of a battle with his "Zantetsuken" ("Iron-Cutting Sword"), instantly killing the enemies by slicing them in half. If acquired before the end of disc 3, Odin will appear in a battle with Seifer Almasy, the only time he appears in a boss battle. However, Seifer somehow manages to reverse the Zantetsuken and bisects Odin with his gunblade. The Zantetsuken is knocked from Odin's hand, and a mysterious hand reaches out of a portal to catch the blade. This is revealed to be Gilgamesh, who replaces Odin for the remainder of the game.

Final Fantasy IX
The Eidolon Odin is used by Queen Brahne after she extracts Princess Garnet's eidolons from her to destroy Cleyra Settlement. Garnet can gain the ability to summon Odin through the item Dark Matter. As a summon, Odin performs his Zantetsuken in the same way he had in previous games, destroying enemies outright. However, if Garnet has the Odin's Sword ability equipped, the Zantetsuken will deal damage to enemies it doesn't defeat outright.

Final Fantasy Tactics
The job class Summoner earns this ability over time.