Although the rest of the journey may not necessarily need this mage, it cannot start without him.
If Sine could really leave, then others could too. And if Encyclopedia wanted to leave, Little Cat might want to, and "Speechless and Invisible" would also follow... In the end, there might be hardly anyone left in the group. It would be better to just disband.
So he kept fanning the flames, forcing Sine to demonstrate his "necessity" in a clownish manner. After doing this, because this old mage values his reputation, he wouldn't take back his words. This way, it's safe for the others too.
Though Vagabond wasn't the leader here, he was the only one who carefully observed everyone's expressions after Aiwass revealed the form of the Son of Si Zhu. A real adventurer who has been through trials for four to five decades has an essential experience difference compared to these occasional transcendent task-takers.
