This event would be something that'd relate more to the past, before Madara was born or rather had taken place in the past. Though, you may already have noticed the similarities between the two bloodlines of Hyuuga and Uchiha, based on theories Sharingan is a variation or a new form of Byakugan. According to characters themselves, Hyuuga is one of the eldest clans of Konoha. Anyways, back to theory section; a long time ago, perhaps even before the creation of Konoha itself a man whose identity was unknown got involved with a woman from Hyuuga. As a result, the woman fell in love with the man and she gave birth to a child named Madara.
Now before we move on I'd like to point a few things out:
Madara's father was the King of Tengu, Sojobo, a Yamabushi Tengu. And the symbol you've seen on Mr. Emo's back is a fan, also known as Uchiha. It is said that Sojobo, as the King of Tengu's had the a few abilities, such as telepathy, teleport and creating a storm. Teleportation: Kakkashi used it in a battle with Akatsuki, he teleported the opponent to another dimension as he exploded himself. Telepathy is where Itachi invaded Kakkashi's mind. I myself have yet to notice any storm so I can't give you any referrence at this moment. Now back to the theory section:
As Madara grew older his father became interested in taking over his body (kind of like what Orochimaru does--- though some claim that was Sojobo's true intention to begin with--- as in he married the woman to create a new container. I will not deny the possibility, but won't claim that's to be the case either. I'm thinking that his father feared Madara than anything else.) Thus Madara summoned Nine tail (or some claim that he made a pact with him, although if you compare the summoning process and making a pact, you'd see there's little to no difference at all between the two) and used its powers to grow stronger. However he still was not able to defeat Sojobo and thus sealed him up. Now to unseal him three MangekyouSharingan users are required. Now to go back on what franzoir stated that you were confused about: The true purpose of Uchiha clan, according to Itachi's behavior and way of thinking, is to unseal Sojobo and grant him a container of some sort, just like what he desired. Now who these three MS users are? Well Itachi and Emo are two of them, Madara is probably the third one, but Kakkashi in a way is a MS user too. Thus we don't really know at this point. (But it may be Madara, since Itachi is unaware of Madara's true identity.) Another thing to mention, while we're at it is that while Madara is taking the risk of being killed just by participating in such exercise or rather activity to unseal what he had sealed in the past, you should think about the fact that he's building a new weapon using the Tailed monsters and thus, by completing this weapon he may hold enough power to defeat Sojobo and possibly take over his body or gain his abilities. Unseal him just to kill him? Well if you were used all your life too you may have done a similar thing.
I believe this person has done a better job explaining the series of events or the so called history of Uchiha.
Source?!
Edit: You should check out the last post made by that person, he made a lot of good points with those pictures, although I'd say if you hadn't already noticed them from previous chapters, then you're a failure, an exceptional failure whose life is dedicated to failing.