tell me the forebidden lore

Actually played it last week with a friend so I can provide the most recent update on this. She played as the guitarist and was named "Umbran Lass" but spelled out using a bunch of symbols/accented letters so that there weren't any traditional English letters in her name. I literally cannot recreate it using my phone keyboard. She was a mysterious woman who appeared in Amsterdam in the late 1980's with no birth certificate or proof of identity and began doing shows around the city where she would just put her guitar against the amp and let the feedback give the crowd headaches. They would go home and have vivid nightmares. Eventually she was joined by a strange and extremely timid (but huge and ripped) man named Güther Shadow who speaks for her when setting up shows with venues. In truth he's her thrall and he helps her spread her unknowable message by singing the same two songs (My Name is Jonas by Weezer and Creep by Radiohead) over and over again while on the verge of tears and begging the crowd for help. They assume it's part of the act. The crowd still goes home and has horrible nightmares, but now that Günther is involed Umbran Lass consistently appears in them and speaks messages that cannot be remembered upon waking up.

never have i ever wanted to watch an fictional documentary about a fictional cognitive-hazard band until now.