The Origin of Black Spirit #4

However, if it had to stay for a longer period of time, the Specter prepares to seek out the black stone NPC Knowledge Item on its own. The Specter over-awake the creature's brain and amplify the brainwave in order to grow much faster, while collecting information from the creature's memories and conscience.

When the Specter is about to come out of the creature's body after it has acquired a shape, it imprints in the creature's head that it is the creature's calling to find black stones.