I think you should read your previous post, it's already been answered..
Dont know exact chapter but he leaves the 9th mountain and while in the 8th mountain he makes a enemy out of a Dao Lord and then that Dao Lord calls some others to help so like 3 or 4 Dao Lords and him fight but even MH cant beat that many so he runs away and ends up having his body possessed by a super expert from a long time ago and MH is supposed to be dead. New guy improves MH's already strong body and his treasures like the spear and the lightning cauldron but accidentally activates the 4th Nirvana Fruit. So new guy goes after all the nearby cultivators including Dao Lords chasing MH and absorbs them to feed Nirvana Fruit or it will kill him. MH reveals himself and says he hid his soul inside Nirvana Fruit and absorbs the guy who possessed him. This stabilizes 4th Nirvana fruit and he spends the entire Meng Clan arc fully absorbing it reaching a level comparable to Dao 5. At the end he fully absorbs it and steps into his Ancient Realm tribulation