I chose...

"There was a Soul Inheritance inside the mysterious circle!"

Everyone's heart skip a beat when the name of Soul Inheritance sounded. 

Dead cultivators left behind inheritances, and they were extremely rare. 

Typically, a real inheritance was based on cultivation technique, skills, arts, weapons, and different wealth that the dead cultivator accommodates throughout his entire life cycle. 

When a cultivator didn't find someone suitable to pass on their heritage or was injured by someone to the point of death, they create an inheritance ground to pass on their legacies. Inheritance grounds have also a second name, Cultivation Tombs! 

However, these inheritance grounds weren't just walk-in-the-park, they were extremely dangerous most of the time and if you by any chance enter an evil cultivator's tomb, there were more traps than treasures.