Cultivators in the World of Cultivation are extremely difficult to raise, consuming copious amounts of resources and requiring a long time, and once one is lost, it's very hard to replenish. So, after the war entered the deadlock phase, a gap in talents began to emerge in the World of Cultivation, and they gradually couldn't withstand the assaults of the Outer Demons.
Under the relentless battles that spanned nearly a millennium, both sides suffered massive casualties, which included the loss of some relatives of the higher-ups from both fleets, thus entrenching an irreconcilable vendetta. If the World of Cultivation were to be defeated, the entire race of the World of Cultivation would be completely obliterated by the Outer Demons, and our kind would cease to exist.
