In God of War series
In the Kingdom Hearts series
Sora will arrive in the Olympus Coliseum and meet Phil. A small humanoid creature that will try to train you regardless of Donald's and Goofy's claims that you are already a hero. You will then meet Hades that will give you an Entry Pass to participate in the tournament given in the coliseum. In that tournament you will fight strong and famous foes including Cloud and Cerberus both sent by Hades to destroy Hercules (and you on the way).
This world is small with only two main areas, the entrance and the stadium. You will spend most of your time in the stadium, either for the fights or for some cutscenes explaining you exactly how Hades wants to kill Hercules. The entrance is where you will meet Phil and have the rules of the different tournaments going on with a leaderboard. Even once the story segment is done, you will sometimes receive a notification of a new tournament available (you will need to complete the previous ones first) and try to compete to be the best.
In Chain of Memories, the Coliseum is in the middle of the 'Olympus Coliseum Survival Cup' when Sora and his friends arrive. So Sora decides to join the Tournament as there is also Hercules competing! Hades will find out about the tournament too and will hire Cloud (again like the PS2 title Kingdom Hearts) to kill Hercules in exchange for his memories. Sora and his friends will find out about Cloud and defeat him but Cloud will run away. Sora and his companions wil follow him and find Cloud defeated by Hercules himself but Hades will interfere and attack Hercules. Sora will jump between them and fight Hades. Once defeated, Hercules will thank you and Cloud apologize.
In Kingdom Hearts II, when landing in Olympus Coliseum, Sora and his friends will be welcomed by their good friend Hercules. They then enter the Underworld when, stumbled upon Megara. Down in the Underworld, Hades is again trying to get rid of the powerful Hercules. When back in his 'lair', he is among summoning Auron (from Final Fantasy X). Hades has giving him orders to defeat Hercules. Refusing to obey Hades orders, Auron turns against him, and Hades is now trying to kill Auron. When this scene starts, Sora,Donald and Goofy arrive and decide to take part of this fight against Hades.
However, Sora will soon realize that his powers in the Underworld are nothing compared to what they are in the living world. After they noticed this important fact, Sora, Donald, Goofy and Auron decide to make a run for it, but Hades catches up to them, and goes into 'Berserk Mode' and starts to summon heartless and throwing fireballs. When trapped by Hades's magic wall, our friends have no choice but to fight the group of heartless that surrounds them. Once done, the barrier breaks and they move to the next area.
After a few fights, Sora and his friends finally reach the Coliseum again and things go no better, as they are locked in and Hades summons Cerberus. With Donald and Goofy safely in the next area, Sora and Auron are forced to fight Cerberus alone. While this is going on, back above inside the Olympus Coliseum, an enemy called, Hydra, is destroying the whole Coliseum. Hercules himself is powerless in front of such a foe. Sora and his friends will however finish off both monsters saving the Coliseum once again for this time being...