The series also introduces Spectrum, who will be relevant to "The Marvels" film, which premieres later this year.
Spectrum is the hero name for Monica Rambeau (Teyonah Parris), the daughter of Captain Marvel's (Brie Larson) best friend Maria Rambeau (Lashana Lynch).
Since we last saw Monica in "Captain Marvel," she's grown into an adult. However, "WandaVision" episode four explains that Monica temporarily died after Thanos wiped out half of the universe in "Avengers: Infinity War."
She returned, of course, with the rest of the people resurrected after the Blip. However, during that time her mother, Maria, died of cancer.
In "WandaVision," Monica returns to her job with SWORD and accidentally gets sucked into Wanda's recreated world in Westview. After being thrown out of the world by Wanda in episode three, she forces her way back in episode seven and is given powers in the process.
While we do not get to see her full range of abilities, Monica will return in "The Marvels," alongside Captain Marvel and Ms. Marvel (Iman Vellani), where we may see her more in action.
In the mid-credits scene in the "WandaVision" season finale, Monica is last seen speaking to a Skrull, who teases that the new hero is about to go to space, which is probably how she comes into contact with Captain Marvel.