The Sentinel/Guide trope came from the 1996 TV series The Sentinel, where the protagonist is a detective who developed supersenses in the Peruvian jungle! He has a partner who helps him keep his abilities in check, but if I'm correct, the whole Guide name and lore were created by fans inspired by the events of an episode. I found the trope description on Naver while researching Pistilverse – and as for Pistilverse, an ARMY tweet about it went viral in 2022 and that's how I and many others found it. They are fascinating concepts to explore if you want to go beyond Omegaverse.