He is very weak compared to a world god. That's why he had to expose some of the secrets of Legion or the sage wouldn't have taken him seriously. In fact, the sage might have decided to hunt him down immediately. There wouldn't have been any negotiations. The sage could send thousands of Origin gods after him and they will kill him again and again until his mind actually fractures from the deaths.
The sage is scheming and pragmatic at all times. Soverick had to avoid the fate of being hunted down by showing the sage how difficult it will be to end him. The sage could end him but he decided not to do so because it will take a lot of resources.
And antagonizing Soverick means antagonizing whatever entity or entities Soverick is. The plane will take the brunt of the clash between the two of them. The first sage certainly doesn't want anything bad to happen to the plane so that its performance during the era of conquest will not be hindered.
