The old man insisted that they stay for a few more days so that they could come up with a plan to capture the Wolf Imperator. The Fire Sage fund this very suspicious. The old man had become too interested in their matters to the point that the Fire Sage felt dread well up in his heart over the matter.
He agreed to stay but he was no fool.
He used the time to investigate the best way to escape the Sage Guild.
He understood that if he were to just decide to leave without a convincing explanation to the old man, things could become problematic.
The Fire Sage was clear on the power difference between him and the old man. He was in the God Realm but from what he had heard from the other worker of the guild, the old man was a Supreme Celestial. This was the realm above the Celestial Realm.