Du Yi had tried some before, and when he saw the hallucinogenic effects, he stopped immediately. As Misha said, this stuff was addictive and could even immerse one in a virtual world. Consuming too much of it was basically suicide.
If it wasn't for controlling Elder Tengyuan, Du Yi wouldn't bring out the Celestial Cream.
He knew the power of the substance himself and worried that if the formula got out, malicious people would manufacture it en masse, causing countless harm. As for the formula, Du Yi kept it to himself, not even telling his two partners. Only this once, Du Yi told himself. Just to achieve his goal, only this once. Once he had what he wanted, he would stop.
