WandaVision has given us our biggest clue yet over who the real villain is

WandaVision can't seem to decide who the villain of the piece is. Is Wanda doing everything herself? Is there someone nefarious pulling strings in the shadows? And might the Big Bad even be familiar to MCU fans or only to those who know Marvel's comics inside and out? So. Many. Questions. Thankfully, WandaVision episode 6 seems to have narrowed down the identity of the real villain with a handful of minor lines that might have slipped you by.

Spoilers for WandaVision episode 6 follow.

One of the most prevailing theories so far is that one of Westview's residents could be Mephisto, Marvel's answer to the devil. The lord of fire and brimstone certainly doesn't show up in this episode – but one line makes pointed reference to the character and a comic storyline.

"Unleash hell, demon spawn," Pietro yells at Billy and Tommy as they go trick or treating. That could easily be read as the twins getting up to their usual antics but, look a little further, and it could imply that Wanda's ability to have children has come thanks to a deal with the devil.

In the comics, Wanda was only able to have Billy and Tommy by using fragments of Mephisto's life essence to bring them into existence. They are, quite literally, spawns of the devil.

But Marvel loves a spot of misdirection – this could be nothing at all, other than throwing a bone to Reddit theorists and those who think they've cracked the code. The studio has even muddied the waters with another villain namecheck this week.

In this instance, the word "nightmare" was uttered twice in the Halloween-themed episode. On its own, it's not much – unless you know your Marvel history. 

Nightmare, the proclaimed Lord of Darkness, is a mind-messing Marvel villain from the comics who has long been considered to be in the running for a leap to the big (or small) screen. He typically preys on the victim's biggest fears and, as we've seen so far, Wanda's grief has gotten the better of her on several occasions. So, out of nowhere, two big candidates have suddenly been directly or indirectly referred to.

But one potential 'villain' who could be out of the picture is Kathryn Hahn's Agnes. While the long-running suggestion that Agnes is actually sorceress Agatha Harkness, a magic-user from the comics, it was revealed this week that she, too, is seemingly being controlled by Wanda and has a separate identity as a Westview resident.

Whether that's a trick on Agnes' part or not, it appears that the pool of potential villains is growing ever smaller as WandaVision starts to zero in on who the real baddie is.

Catch up on the MCU story so far with our guide on how to watch the Marvel movies in order and make sure to read our WandaVision release schedule to find out when the show will come to a close.