(Spoilers for episode seven of FX’s Legion below)
In an alternate promo for FX’s Legion the “Yellow-Eyed-King” is revealed and it’s none other than the Shadow King.
In the most recent episode Lenny told David that his father didn’t want to meet him and there’s a reason. Charles Xavier has a decades long rivalry with Shadow King in the comics and the “King” is responsible for both Xavier’s paralysis and his formation of the X-Men. Shadow King is an extremely powerful psychic entity. While there haven’t been any videos teasing the arrival of this character there is a low-res version you can find here.
Legion episode seven will be airing this Wednesday.