Brother Sepdifer is neither a fan character or in the comics. The truth is, he originated in one of the Stone Arch DCU books made for children: “Battle of the Blue Lanterns”. He and Saint Walker are the Blue Lanterns present within the story, though Sepdifer does not speak a single word throughout the book. The in-story reasoning is because -according to Saint Walker- Sepdifer is taking a year-long vow of silence as a means to show his devotion to the power of Hope. Per recruitment protocol, he was selected by Sister Sercy to be the next Blue Lantern after her.