so people actually solved purely on trial and error earlier?
First solution was found by looking at the game's code, and tiny bit later someone figured it out that you need to use other four puzzles in the Heart of Mystery as a "legend" for the main one. Turned out, this leap of logic was never needed, since data from secondary puzzles fill slots on main one automatically, when not bugged.
You don't need all of them. On my first run I know for certain I missed the notes in Iz and still got the Storyteller to decipher the damn thing.
Afaik, there were several extra pages in early versions of the game (in Gwerm mansion for example), but Owlcat patched them out at some point and now you need to find all, including some obscure pages, like correctly deciphering Vrock note from Molten Scar.
Plebbit says you need 19 notes to finish the quest but all 20 to auto solve the lexicon, meaning that you will only decipher it at Threshold because that is where the last note is. I could always try to fish for a 20 on the skill check but I am in no hurry.
1. Fishing for 20 on Skill check is useless in Pathfinder - there is no Critical Success for skill checks here.
2. I have read Lexion on character with zero Lore investment with some egregious buffing and items like:
- +10-15 Competence from items, there are items with +10 version for all Lores, and +15 All Goggles from Crusade Management choice.
- +4 Food
- +8-10 Sosiel's Touch of Good, maybe Madness Domain buff
- +Int and + Wis Items and buffs for extra +2-3
- +3 Insight all Lores robe from the Cold Waters quest
- +4 Morale Higher Heroism
Put Brilliant Inspiration (Bard lvl 6 spell, there is scroll in Blackwater) on top, get some Luck Hex and you will barely need reloads even for the dumbest MC in creation.