End-Game Tome
1) Go to thousand streams and purchase script of fate x3 when the price becomes 10,000,000 gold coins for script of fate via commission shop preferably.
2) Take a look at Nature's forge via Fate tab and at Upgrade Tome forge via level 6 at last tab you will notice the requirement for Pan Gu Tome as one of the level 6 Tomes.
2) Manufacture any 2 level 5 Tomes which matches your class's build at Nature Forge and the third will be any of those that can be upgraded to Pan GU Tome. [Note skip the rest of steps if you are satisfied with level 5 Tome alone]
3) Decompose the first 2 level 5 Tomes Manufactured via Upgrade Tome Forge as they give together around 81 old book of principles x2 and use The Third Manufacture Tome in our example we will use VoidLand Tome to upgrade it at last tab of Upgrade Tome forge to Pan Gu Tome
4) Afterwards you will need Bookless Transcript to turn your level 6 Tome to one of rare Tomes at advanced forge tome. The cost goes around 100,000,000 gold coins.
5) Now the real deal comes. At North platform of Archosaur via Nation war Tome forge the rest will require supply tokens to get all required materials via contemplation forge. You will have to turn your tome to dominance then to Emperor tome. Recommendation: Never refine any of the tomes except the Emperor Tome.
Credits: Special thanks to Celea [known as SagaCaerlea] for the information.