The reason it was precious to such an extent was, on one hand, that Universe Gods of the 'Void Realm Illusion' were exceedingly rare. On the other hand, soul-path secret techniques were simply too terrifying!
For example, the 'Void Realm Illusion'.
What did an illusion at the tenth level of the Chaos Realm signify?
One had to know that a large number of Chaos Realm tenth-level experts, including Dongbo Xueying and Yingshan Matriarch, relied on external power. For instance, the Southern Cloud Sacred Body, the Red Cloud Divine Spear, and so on... If they relied solely on their own Chaos Realm cultivation, they would at most be at the ninth level. They had to depend on external objects to unleash tenth-level strength. Their soul strength was roughly comparable to that of ninth-level experts in the primal chaos void.