Challenge by: reminiscent-afterthought
Another one of my crazily long and complicated challenges based off some game or other. :D This one is Yu Gi Oh! World Championship 2008.
Certain things, "events", have to be done in order for the game to progress, so these tasks are also compulsory for you. Others are "side-quests" which aren't compulsory at all, but may assist depending on what you want, and "opponents" where you have a minimum compulsory (equivalent to racing through as fast as possible) but no maximum (where you roam to your heart's content). They also have a 50% win rate, so flip a coin again and if heads, you win; if tails you lose.
Your goal? To beat the game of course. :D And win the championships. There are actually two parallel things. Passing certain requirements in the game will allow you to unlock more characters in the championships. All is explained in the doc, so don't worry.
Your first stop is registration. Just follow the contents and work your way through the world. Enjoy!
Note: currently written up to end of world of grace/easy tier.