The reason why Lin Huang left the two Black Abyss members to Zhao Xuan of Royal was because he did not have a method to interrogate them.
If he read their memories, it would trigger the Abyssal energy in their heads.
The outcome would be the same if he hypnotized them. The reason being was that hypnosis' nature was also a psychic technique.
They could only interrogate those two, getting them to voluntarily reveal the information in order to avoid triggering the Abyssal energy in their heads.
Regarding techniques of that nature, Lin Huang was definitely not as well-versed as the professionals.
Secondly, he left the two behind intentionally; he had also left an imprint on their bodies.
He figured that there was a high chance that the Black Abyss would send heavenly dao-level powerhouses to rescue the two of them.
