Wang Yu stared at the banner in his hand, his thoughts racing. Suddenly remembering something, he flicked his wrist.
A howling sound immediately rose from the pitch-black banner, and streams of black miasma gushed out.
Amid the billowing black miasma, three single-horned ghost creatures emerged, each over ten feet tall, with blue faces and protruding fangs.
They were precisely the first-tier yin ghosts formed when yin spirits advanced.
These ghost creatures were, of course, not the first batch of yin ghosts born within this banner.
The entry-tier yin ghosts born by devouring living souls back in the Blue Star World had long since been devoured completely by the stronger living souls that emerged afterward.
These were newly born yin ghosts, formed through the yin spirits devouring one another after Wang Yu returned to the Cultivation World and released the seal on the yin energy within the banner again.
But he had only been back in the Cultivation World for a little over two months, and he had placed the Yin Soul Banner in a place rich in yin energy to nourish it only about half a month ago. How had yin ghosts emerged so quickly?
Moreover, he had yet to put any living soul iron into the banner's inner space.
Could this second-tier Yin Soul Banner also have a special effect that accelerated the birth of entry-tier ghost creatures?
Wang Yu looked at the three yin ghosts before him, then at the Bone Banner in his hand, and fell into thought.
He could roughly guess why the Yin Soul Banner had advanced into a second-tier magical artifact. It most likely had something to do with the batch of entry-tier ghost creatures born within it in the Blue Star World.
After all, among the Yin Soul Banner's advancement methods, there was