Destruction of the Nine Nether Sect.
Gu Qingyang naturally did not act because the sect was part of the Demon Race.
In fact.
Gu Qingyang no longer belonged to the human race, nor to the definition of the Demon Race in the Immortal Extinction Realm; he was a being on another level.
If one had to categorize, Gu Qingyang saw himself as equivalent to the Innate Spirits of myth and legend.
Therefore.
Gu Qingyang destroyed the Nine Nether Sect, not because it was demon-related.
In Ye Jiuyou's memory, all the cultivators who joined the Nine Nether Sect were actually wicked individuals, often capturing humans and isolated demons to nourish themselves with their flesh and blood, cultivating Demon Techniques.
For such cultivators who wantonly harmed their fellow beings, Gu Qingyang would never show mercy.
Moreover, they intended to deal with his followers, adding to their sins.
Destruction of the Nine Nether Sect.
