IT'S ALIVE~~~~~~!!! This was obvious from the first still shot, but it's nice to have it confirmed. I'll be very surprised if this statue doesn't end up becoming part of Wapurgisnacht's body somehow (specifically, the doll portion). Obviously it will have to undergo a magical girl transformation to get to that point, but right now it's a blank slate that could theoretically turn in anything.
...that said, it would be so fucking funny if this is how we get the giant Mami head from the concept movie, can you imagine? Although if so, I suspect there are probably some intermediary steps, i.e., it might look like someone else first before Mami co-opts it. Or maybe Mami was the real villain all along If so, all hail our new Mami overlord! I say we hear her out. :)
Anyway, Walpurgisnacht appears to be made up of:
A doll body (which might the statue in the Nazukakotsune, TBD)
A big old Cog Of Unyielding Fate (the symbolism is not subtle, lol)
A dress evocative of Homura's contracting outfit (out of universe, it's the other way around but whatever)
...all of which is turned upside down to symbolize this is the opposite of how it should be.
Given that the Nazukakotsune is filled with books labeled "Witches" with Walpurgisnacht's face on them, I'm inclined to think that Walpurgisnacht is made from the non-human portions of the Law of Cycles, and is what happens when all the witches in the books "get loose" and recombine into a different kind of entity, one "upside down" from the initial configuration. She's not just any old bunch of witches, she's all of them, throughout space and time, every one that was collected by the Law of Cycles, and thus is a concept who exists out of the normal rules of space and time just like the original Law of Cycles.
Furthermore, causality probably goes the other way, too - just as Walpurgisnacht was made from the Law of Cycles, the Law of Cycles was made from Walpurgisnacht, resulting in one big loop or series.
The fact that Walpurgisnacht's dress resembles Homura's contracting outfit also suggests that some or all of Homura's system maybe a part of her, or it is representative of some aspect of Homura that is incorporated into it. Who knows, that particular Homura dress might have changed in later iterations, but it seems odd to me that they would look so similar if there wasn't intended to be a connection on some level.
In other words, depersonalized and inverted Law of Cycles + Homura's system + Fate = Walpurgisnacht, at least the portion of it we've seen before. But I do not think the main Walpurgisnacht body has a human will or intelligence; the human aspect driving it is embodied in Evil Mirror Homura. I expect that "Wasu" and Walpurgisnacht will remain separate entities throughout the film despite being connected, similar to how we've seen Sayaka and Oktavia manifest separately. Just as "the Law of Cycles" can be divided into two parts, the same is equally true for her evil counterpart.
I've always thought that the reason why Walpurgisnacht always comes to Mitakihara is because she's drawn to Madoka - either because Homura's wish was to see Madoka again, because the Law of Cycles component is instinctively trying to reunite them, or both - and the whole thing is one big chicken-and-egg problem of universes being created and erased and causality getting tangled. In other words, Walpurgisnacht's initial appearance in the original series isn't random chance; it's fate. It had to happen because on some level, it already had.
Urobuchi's general philosophy re: time travel is that the past cannot be changed because it has already happened and any attempts to undo it either won't help or will actively make things worse, but a better future is still possible, and it can only come about by understanding the true nature of the world first. To translate what that means for this movie: things have to get a lot worse before they can get better.
