Cerberus
In Greek mythology, Cerberus, son of Typhoon and Equidna, was the guardian in the gates of Hades, the realm of the dead. In appearance, Cerberus was a gigantic size of a dog, which had three heads (or 50 according to different versions), a snake tail and on his back and thick layer of snakes heads. Its mission at the gates of the kingdom of the dead was to prevent any alive human being infiltrate in Hades realm, if needed, killed anyone who tried.
Only two person who able to go through Cerberus. First is Orpheus, who play beautiful music that able to sleep the dog and and step through into Hades to rescue his beloved, Eurydice. And Hercules, one of the twelve work given by commissioned Euristeus who must take Cerbero to Micenas. Once such a feat, Hercules was forced to return to the gates of Hades, because Euristeus was petrified to see such horror in his eyes. In Final Fantasy series, Cerberus appear as summon in Final Fantasy VIII and often appear as mob monster.
Hades
In Final Fantasy VII, Hades appear as one of the summons, and in Final Fantasy IX he appear as on of optional boss in Memoria that able to defeat. Hades refers to two mythological terms, both belonging to the Greek culture. The first is the place where the dead live, as in the Greek culture there is no difference between those who have done well and those who have done evil, unlike Christianity, that the split between Heaven and Hell . The second, and that interests us is the God of the dead. Hades, son of Cronos and Rea and therefore brother of Zeus and Poseidon. Together they defeated his father and divided the world, as you know Zeus rule the land, Poseidon at the sea, and Hades rule the Underworld.
According to the Greeks when a person dies, they conducted to Hades through a large lake Caronte, by the boatman. But before entering the Hades that person was judged by Minos, Radamantis and Eaco because they chose the path that they had to take the deceased. There were three possibilities: The Champs Elysees for those who acted good, plain Asphodels for those who are not well-behaved or not wrong, and the Tatar for wrongdoers, inhabited by the most evil creatures of the establishment. Hades is not an evil god. It's symbol is a helmet that gives invisibility to wearing it and a horn in his hand.
Minotaur
In Greek mythology, the Minotaur was a monster half man and half bull. He was the son of Pasifae (the queen of Crete) and a beautiful Toro (yes, a bull). To become King Minos of Crete had to demonstrate that she was capable to do any deed. In these circumstances Minos asked Poseidon, the god of the Sea, which would leave a beautiful bull of the ocean. Poseidon accepted, but with the promise that Toro will sacrificed when leaving. The bull came out of the sea, and, because of this he became king, but the bull was so beautiful that it could not sacrifice. As punishment, Poseidon did his wife, Pasifae was angry (notice to minors, the party is still a little too much). In her madness Pasifae could not repress her sexual temptations with the beautiful bull and ordered to build a cow Dedalus wood, where Pasifae got to be having sex with such animal. From this Minotaur was born.
The Minotaur is a monster with the head of bull and the human body. When he learned what had happened, Minos sent him to a vast labyrinth Dedalus there to enclose the Minotaur, which would be fed by maids. After some time Teseo, a Greek hero entered the labyrinth equipped with a sword and a tangle of yarn that gave by Ariadne, the daughter of Minos who by that time had already been in love with Teseo. Teseo killed the Minotaur and Ariane confessed that there was almost no resistance. This is because the Minotaur could not understand why he was afraid of the people, since he had never seen his face, and the Minotaur wanted to end his existence and Teseo "helped" him. In Final Fantasy Series Minotaur appear in Final Fantasy VIII as one of the Guardian Force. In this game he appear as Brothers which is Sacred and Minotaur, and their ability was Lovely brother with earth element technique.
Shiva
Shiva is the supreme god of the Hindu mythology. In the appearance and as usual, doesn't have any similarity with SHiva we known on Final Fantasy Series. Perhaps only in its blue skin and in the long hair, but nothing related to the ice. Shiva described as a god who always sitting on a large tiger skin and make the the meditation in Himalaya Mountain. He also described has three eyes (Tri Netra) that able to see through three world Bhur (Underworld), Bvah (Earth), Svah (Heaven). Shiva usually equipped with fuses or snakes as well as his bracelets. He was also said that his long hair flowing through river Ganges (Gangga). He was often represented alongside his trident and timbal, and has two legs and four arms.
Shiva is also known by other names such as Mahadeva, Sundaresvara, Natajara, Rudra or Baraiva. These names have meanings in Hindi as varied as "rugidor", "Lord of the Dance" or "Mr. Beautiful" among others. Shiva has a goddess wife named Parvati. They have two children, Skanda represented as a man of six heads and six arms and Ganesa portrayed as a woman with head elephant. In Final Fantasy Series, Shiva appear as one of the basic summon with it's sexy appearance and powerfull ice element, that will frost all enemy who faced her.
Odin
Odin is the supreme god of Nordic mythology, he is the son of the giant Burr. He is a dark and evil god, able to revive the dead. His role was same like Zeus in Greek mythology. He was often represented by a long blue cloak covering his body, with a hat and an aged appearance. He lacks an eye because it is pulled and he left the giant Mimir (protector of good and wisdom as the Germans myth) as a pledge to stop him drink from the source of wisdom.
His most prized possessions are his horse Sleipner, son of Loki, which is Grey and heavens horse riding on his eight-legged, his spear Gungnir (forged by the children of Ivaldi) and his ring Draupnir. His best companions, aside from his steed eight legs are Huginn and Muninn, her two black crows that collect information throughout the world for their god and his two wolves: Geri and Freki.
Odin was associated with different women, which raised five children: Thor, Balder, Vale, Vali and Vidar. Odin alongside with his brothers (Vili and Ve) was able to defeat the dominant giant, Ymir, and use the parts of Ymir's body to created the world as we know it today. On Ragnarok which is Final battle between the god and the monsters, Odin dies on Fenrir. On the other story Odin also have lot's of virgin maiden battle servant called as Valkyrie. In Final Fantasy series, Odin appears as one of the most powerfull summon, with his "Zantetsuken" technique that will slash all enemy into pieces.
Diablos
Diablos is Devil, also known as Lucifer or Satan that mentioned in the Bible and the New Testament. Diablos defined as the arch rival of God and the temptation for human. He is the most powerful of all the fallen angels and was expelled from heaven because of his arrogance.
His appearance or representation looks like a red creature with a long tail and thin just pointed and two horns on its head, usually associating the trident. Anyway, in the Christian culture, countless times that the Devil can be presented in front of indefinite forms of a human being, not only physically but in the form of temptations, dark desires ... Who will try to lead the victim "the wrong direction". His appearance more or less consistent with that shown in Final Fantasy VIII, where Diablos is a creature whose appearance reminds us of a fallen angel shape, with two horns and a tail, but in this case does not have any trident. In this game he called as "Dark Messenger" that bring fear to all of enemy that dare to face him.