Experience 

"Ugh… the air really has become foul!" Mo Shi grunted and covered his nose when they arrived in the mortal realm, the S City where the serial murder, which is likely done by an adult Soul Eater, happened. 

"Fortunately for the angels, they weren't sent to handle this case." Yi Bing said. 

Jin Wu nodded in agreement when they recalled how Ling Shiyi was injured after Ling Shiyi was sent to a world which is actually an apocalypse world, that is a world filled with Foul that is coming from the zombies! Ling Shiyi was really unlucky. Not only was he gravely injured, he was also ridiculed not only by the Upper Heaven, but also by the Lower Heaven. No need to include the Middle Heaven, which is Shen Sheng's residence and he is its only occupant. It was Shen Sheng himself who sent Ling Shiyi to that world, so you can guess Shen Sheng's intention? 

Obviously, Shen Sheng deliberately sent Ling Shiyi to a world that is not only harmful, but maybe could kill him.