It has been a long time coming for Wanda Maximoff's powers, their origin, and growth to come into play in the MCU, and WandaVision will be exploring them in full.
For the longest time, all Wanda could do in the MCU was manipulate objects and minds, but now it seems like she can bend reality to her will. The exact origin of Wanda's powers has also come into question, even with Marvel Studios president Kevin Feige himself implying that the Mind Stone “unlocked” her powers instead of directly bestowing her abilities.
However, one curveball thrown at fans has been that all of this reality-warping isn't exclusively the fault of Wanda, and that someone else is affecting her faux world. Nightmare has been rumored to be the villain in Doctor Strange In the Multiverse of Madness, so some fans had assumed that, since WandaVision would directly lead into that movie, Nightmare would appear in the Disney+ series as well.
New footage in the latest WandaVision trailer may point to Wanda having an explosive nightmare.
The new WandaVision trailer features a scene with the blue Mind Stone, originally in Loki's scepter, floating towards Wanda like a Blue Fairy, with Wanda even reaching out towards it, seemingly enchanted by the glow. Wanda can now plainly be seen wearing the same outfit that she wears in the post-credit scene from Captain America: The Winter Soldier.
However, what's interesting about this is that, in that same post-credit scene, audiences are shown the blue gem intact, still having a powerful glow, but with Wanda and Pietro now superpowered.
In this latest trailer, fans are shown the blue gem exploding outwards, exposing the Mind Stone within, and as seen in the second trailer, Wanda was right next to it when it exploded with a brilliant yellow. This is likely the moment that Wanda was given her powers, or had them unlocked, by the Mind Stone, but it might not be a literal interpretation of the event.
WHAT THIS MEANS
Recall that in Avengers: Age of Ultron, the titular villain had to break open the blue gem surrounding the Mind Stone when it was attached to Loki's scepter. In the original Avengers, it was stated that Loki's scepter was powered by the Space Stone, then known as the Tesseract. What it was “powering” was likely the blue gem surrounding the Mind Stone.
It's hard to imagine how, after Wanda exploded the blue encapsulation surrounding the Mind Stone, HYDRA would manage to replace it.
One possibility to explain the WandaVision Mind Stone "origin" scene is that it's actually a sequence from Wanda's nightmare. This would certainly explain why and how the Mind Stone managed to be put back into the scepter in a similar blue casing - it was never removed to begin with. The fact that the Stone itself seems to be floating towards Wanda in her cell with her reaching out towards it like she's in a trance—all very dreamlike.
If this sequence is a nightmare, it could be Wanda beginning to resent or fear her powers after having killed Vision, making her realize that she can use them to bring him back and have a happier life. However, the nightmare could also be caused by someone manipulating Wanda for their own ends, someone like Nightmare, who has been rumored to be the villain in WandaVision for more than a year. In the second trailer, Jimmy Woo seemed to believe that someone was doing all this to Wanda, which could be Nightmare.
Nightmare in WandaVision would certainly be a good lead into Doctor Strange and the Multiverse of Madness, if he is in fact the lead antagonist in that movie.