SAFWY'S ANOMALOUS HUMANS

Hi, I'm Brazilian. I recently saw a video claiming that the *SAFWY* novel features humans who nearly destroyed the Seireitei in the past. It said they possessed immense spiritual energy comparable to captains—energy similar to that of Fullbringers. I’ve since acquired volumes 1 and 2 of the *SAFWY* light novel and would like to know where they appear. I'm running a *Bleach* RPG and want to include them, so I’d like to learn more, but my searches haven't turned up anything about this. I’m also not keen on reading both entire volumes just to find out about them. I’d like to know if they are actually real or just clickbait from the video; if they are real, I’d like to know where they are mentioned.