As far as I can remember, you only need to kill first 2 bosses, then proceed to Red Orcs room, kill the gate, then go to library to spawn mobs that will drop the key to open library room. What I always did was after killing first 2 bosses, I did Drosnin quest to get earring, maybe this Drosnin part is necessary. I can not make a video, I quitted Cabal and only have 1 weak char left