With more than 20 major characters fighting for the spotlight, it was inevitable that some would be pushed to the sidelines. however, once the zodiac pattern was established, it was necessary for there to be a full set of 12 trolls. for that matter, what do Nepeta or Equius do to advance the plot? they were both less relevant that Feferi when they were alive. As for Feferi herself, she acted as liaison to the Horrorterrors, and she is responsible for the creation of the dream bubbles which act 6 relies on. more than that, she acts as a catalyst for Eridan and Sollux’s conflict and it was only through her existence that the Condesce was able to exist. whole the Condesce could have been created as the ancestor for a different Fuscia player, even if they were more useful otherwise it would still be their influence that allowed her to exist. Feferi, as the complement to the other 11 trolls, was certainly necessary, at least as much as any other character.