Tonguez
A suffusion of yellow
I am going to call this right now: There will be no Mephisto. Disney was never goint to put the "Devil" into this show. They theoretically could do a villain with powers, but they'd more likely use Grim Reaper, Master Pandemonium, or even Blackheart, before they'd do Mephisto. They might use Mephisto, Blackheart, or some other "Devil" character in Helstrom, but not here. It would have to be a horror-style show for that. Mark my words.
Yeah I dont think Mephisto will show up in WandaVision either nor do I think Blackheart will be used, but note that a stained glass window depicting a devil is shown in the Loki trailer (which besides the comic storyline, is another reason why people and jumping at Mephisto).
I’m ready to see Nightmare if they do in fact bring in an currently unknow supernatural villain, but don’t think they will.