The greatest and most powerful Dao. One that surpasses all other Dao.
The Dao of Everything.
To train this Dao is the most difficult to train, no matter who it is, what circumstances they have, or who their master is.
Mastering a single Dao, reaching the apex of power with only that single Dao, plowing through that path further than anyone has ever gone before. Then, after dying, master another single Dao in the next life, reaching the apex once again. Doing this 108,000 times, in order to master each and every single one of the Dao while reaching the greatest strength of that era.
As of such, no one has ever trained in this Dao, in fact, no one has ever known about this legendary Dao.
Only one person, Ling Chi, sought to complete the Dao of everything. After his 108,000 reincarnations, the journey of the first user of the Dao of Everything unravels with a man who can do anything.
That was pretty awkward for a kidnapper to ask such from a total stranger. Creepy much. But not the story...wink wink