MCU Phase 4: Every Single Character Confirmed (So Far)
58. Monica Rambeau (Teynoah Parris) - WandaVision

In a strange move, the announcement of WandaVision - or rather the confirmation that fleshed out some more details - also came with the kicker that Monica Rambeau will return to the MCU for it. She was last seen as a child in Captain Marvel, set in the 90s, which is why she'll now be played by an adult in Teynoah Parris for the Disney+ show.
Quite how she slots into all of this remains to be seen, but he was a superhero in the comics with the ability to transform her body into energy after exposure to extra-dimensional energy. She went by the names Captain Marvel (clearly, that's not happening here, unless this really is an extra-dimensional story), Photon, Pulsar and later Spectrum and she has previous with working with Scarlet Witch, having helped her and Doctor Strange battle Dracula.