I have seen enough information and important scenes in order to come to this conclusion.
I have made loads of theories on this anime since this blog began in 2013, in fact the first post on this blog was an explanation for what a soul gem was.
I never understood how madoka could make a wish within a wish for the wish can’t exist without the within that wish? *That’s a lot of wish.* The truth is that Madoka’s wish doesn’t actually exist because in order for god madoka to have power she has to be connect to different realities making her exist outside of the universe however, Homura already exist outside of the universe meaning that madoka only exists outside the universe in one reality (are you guys following this).
In sort: Madoka’s wish is an illusion that exists in a plan outside of the universe.
Like you can see from this image above Homura’s wish created a bubble that gathers all of the different madoka’s power into one place (How can you have one reality with 5-6 realities powering one soul gem).
In order to save Madoka and complete Homura’s wish the two soul gem combine into one creating an ouroboros.
^-o How is it an ouroboros? Because Homura killed Madoka in order to make herself make the wish in the first place, she is and always has been walpurgisnacht.
Madoka get’s her wish to stop people turning into witches and Homura get possession of Madoka’s soul.
*The two of them have created endless power for the universe.*
kyubey punishment: you have to stay in this endless time loop in order to make the contract in the first place.