I got the 2005 Holiday Demo Disc in the mail and this game was on it. When I went to play it, it was so amazingly awesome! Does anybody know the storyline?

Well, only Team ICO knows the storyline. They didn't give it to us so that we would make our "own stories" which has worked. This also makes us want the story more. I will tell you all that they tell us:

Wander and Agro (horse) enter the Forbidden Lands with the Ancient Sword to revive Mono. Upon their arrival, Wander places Mono onto an alter, but it then attacked by shadow beings. However he quickly pushes the sword up and the light beams repel them away. Dormin (god-like entity) talks to Wander telling him that with that sword he can recover the souls of a dead. To do that he must break 16 huge idols which cannot be broken by human hands. Their incarnations are the 16 colossi roaming across the land and you must kill them one by one to destroy their idol. After all 16 are destroyed he will get Mono back. Before he sets out to accomplish this Dormin tells him the price he pay may be heavy indeed, but Wander tells him it doesn't matter.

The only enemies in this game are the Colossus. The shadow beings was a cutscene. You have got to see the ending to this game. Best ending ever.