^ Ok, ok ok, I'll try to put some order here. The story of Rayman Origins is messy as fuck, but I think I discovered what's going on:
( Rayman & friends were sleeping at the snoring tree and then got caught by the livid dead, one of Bubble Dreamer's nightmares. The livid dead people were so angry that they decided to stop happiness in rayman's world, and with the help of more evil nightmares, they caught all of the electoons and nymphs to produce tons of chaos. The only way to stop the evil forces to which the Bubble Dreamer fears is to slap them and amuse the Bubble Dreamer. The reason of their travel is to save the electoons, the nymphs and to kill the nightmares.
Coincidentally, the Magician appeared after a lot of years, and asks rayman to gets those precious shiny creatures called Lums as he travels, so he will give him some electoons in exchange. Rayman, unknowing the Magician's purposess, doesn't care and accepts the offer so he would help the other electoons. Rayman trusts the Magician, so there's no reason to fear what would happen to the poor lums...right?
When all of the nymphs are free, they say that there's a huge evil force at the top of the mountain. Rumours around the Glade of Dreams say that Mr Dark was back. Mr Dark is Rayman's nemesis, so he totally forgot about the Livid Dead people and decided to go to the top of the mountain and defeat him. To get there, Rayman needs the help of the magic from the kings of all of the lands. Sadly, those kings were turned into nightmares by the Bubble Dreamer's bad dreams, so it's up to Rayman to defeat them, turn them back to normal and then ask them for help to get to the mountain.
After that...THE REVEAL! Rayman discovers that the evil force that he was trying to find was always to his side: the Magician. According to some info, the real Mr Dark died a long time ago, but nobody knew it, only the magician. The magician was so amazed about the power of those little lums that he totally freaked out and left Rayman for a lot of years, to investigate their power. Then, he made a decision: he would be the next Mr Dark, and create an impressive steampunk world with gigantic machines and robot security guards. That's right, the magician betrayed rayman for power over-dose, he didn't want to be good anymore.
According to the daily bubble, those machines were designed to control the weather of the glade of dreams, so that's basically the magician's purpose: to use the energy of the lums that he stole from rayman to feed his weather-control machines. After Rayman kills the Magician and destroys his evil empire, he, globox and the two teensies decide to take a nap... but they forgot about the Bubble Dreamer's primordial nightmare: the Livid Dead. Since the nightmares were weakened, those grannies can't do anything underground, so it's optional to kill them. If Rayman decides to stop the nightmares at 100%, then he should get the Skull teeth to bribe the Grim Reaper so he would let them pass. After defeating all of the grannies and crossing the land of the livid dead, big mama appears. When rayman defeats her, he discovers that she was a lost nymph, possibly, the nymph from the Land of the Livid Dead, and then, the story is cut. I don't know what's next since the guy stopped the playthrough during the credits, but if it ends like that, I may suppose that the lost Nymph helps Rayman to clean up the nightmares from the land of the livid dead.)
THE END.
Ok, my brain hurts, gonna sleep...
EDIT: OH SHIT! I didn't know that microphone thing, spiraldoor! that would be helful for the plot too.