Pausing for a moment, Yuan Manqiu said thoughtfully, "No wonder we never found any ghosts after the big explosion. The staff and students at the time were all at the high level of the Refinement Stage or even the Building Foundation Stage. Some of their souls should've been strong enough to survive the explosion.
"Based on your discovery, I assume that the blast was so intense that most of the souls were vaporized instantly. But some of them were too obsessed and thus turned into Phantom Entities.
"At that time, the spiritual energy inside the crystal reactor had all leaked out. The center of the explosion was the warehouse of crystals nearby.
"The crystal reactor itself was meant for the storage of spiritual energy. It was very solid, which made it the best shelter after the explosion.
"So, the Phantom Entities hid themselves inside, until they're discovered by you today."