When I played Olympus Coliseum, I had a blast! "Hercules" was/is one of my favourite Disney movies, and I enjoyed playing around in The Underwold. Hades is still a ass :P But yeah on to a min-ramble about Demyx;
When you first meet Demyx here Sora is all ready to fight, and Demyx just runs by saying like "run!" XD then when you meet him again he is all like "I don't want to fight" (yet he still has full powers) and reads like these instuctions; something like if the subject does not comply then to use force...it's on this little white card :P Then you have to defeat 100 Dancers (his Nobodies, like Axel has Assasains and Roxas has Samurai). Then he is all like *portal away!*, dropping the...oh what was it called....Olympus-Stone-thing? it's a talisman with a cloud&lightning-bolt on it. It makes it so you don't get weakened by being in The Underworld.
Then you meet Auron and like fight Cerberus and have to escape The Underworld while being chased by a massively hard and powerful Hades.
And like things like Meg getting kidnapped and Sora accidentally unlocking The Underdome(is that it's name?), to save her. Then you like fight Pete aswell...
When you finally make it through that, you find that The Hydra is still alive and then you enter this long Boss fight to defeat it by chopping-off it's heads and dropping urns (Urninate! >.> The name of the Reaction attack-thing, that I read as 'Urinate' when I first saw it) on it's back. Oh and you get to fly on Pegasus (wrong Greek-myth though...) and like...it's cool you smack the Hydra's heads in the face while flying ^^;
Yeah after that you have to go to Disney Castle.
It's full of Heartless and you get to Queen Minnie and then you have to wade-your-way back to the throne room and then make the tedious sprint to the throne while using Reaction attacks with Minnie so she doesn't die...Turns out there is a 'Keystone of Light' under the castle. It is supossed to prevent Darkness from being able to enter the castle. But oh-noes! There are thorns all over the place [like from "Sleeping Beauty"]!
Merlin arrives and is all "BACK TO THE PAST!" (only Sora, Donald & Goofy only realize that fact later). Pete in his despair found a door to Timeless River, and thus he is sent by Malificent(sp?) to go and destroy The Keystone of Light. Pete really just wants to relive his grand-ol' -days as a steamboat capn'...I'm forgetting what the Pete character's full name is....I keep wanting to say 'Box-Car' but that is completly wrong ^^;
You are now all retro and Sora has massive teeth ;P (I wish the cow I remember from the old cartoons played a bigger part now-a-days... -_-;)
Yeah you get there and random stuff happens and you need to clear these various portals like one is a burning-building you need to defeat savage cars at, while preventing living fires from making the blaze worst.
I liked the one where you had to protect furniture from being sucked into this portal including a Christmas tree ^^;
Yeah after this is done you have to rescue The Keystone from Bad!Pete with the help of Good!Pete, and board the steamboat. Oh and you need to rebound garbage that is being thrown at you back at Bad!Pete.....
Now that I've beaten that stage I can ether go to Port Royal with Luxord :3 or Atlantica....or go fool-around in The Underdome >.> *thinks most likely Atlantica then The Underdome*...