Shang weighed his options for a bit.
'Should I kill them to keep my secret?' Shang thought.
Shang was willing to make friends, but he wouldn't risk his life.
In fact, he was already surprised that he had decided to put the lives of Astor, Elver, and Sarah above the knowledge he would have gained from the Poison Adept.
If Shang had let the Poison Adept kill these three, he would have been even surer about his victory.
Shang would have only needed to act like he was running out of Mana and maybe get hit by a bit of poison on the way.
Then, he would have simply asked the Poison Adept to tell him who had commissioned him before his death.
With the Poison Adept's arrogant and talkative personality, he would have probably spilled the beans.
But when it came down to it, Shang had decided to save the lives of the three hunters.