I don't know for sure as I haven't read it. But surely the great mage himself is a main character. There might also be some current mages in the world he returns to who play important roles, either as allies or antagonists.
The main character is of course the great mage who returns after 4000 years. There could be a young apprentice - type character who becomes his protege and learns from him. And there may be a powerful wizard or witch who is in charge of the current magical order and has a conflicted relationship with the returning mage, seeing him as both a threat and a potential asset.
In the 'great mage return after 4000 years novel', the central figure is the mage who has been away for such a long time. Besides him, there might be characters like the leaders of the magical guilds in the present time. These leaders would have different reactions to his return. There could also be a group of adventurers or researchers in the magical world who cross paths with the returned mage and get involved in his story. Maybe there's a character who holds the key to some mystery related to the mage's past and their encounter helps to unfold parts of the story.
Chapter 136, "Buying Information", is the clearest early answer because it turns Damien's situation into a concrete plot event. The setup is Damien stood in the modest cottage he had rented, staring out the..., but the pressure keeps building through It had been two years since he had last walked among civilians.. Once the chapter lands on Summon Luton." Damien whispered as he raised a hand slightly,..., the chapter closes with For now, though, he had a direction.
Chapter 486, ", Only You, My Friend", is the clearest early answer because it turns Gu Hang's situation into a concrete plot event. The setup is Riding inside, deep beneath the Imperial Palace, the track twisted..., but the pressure keeps building through After leaving the railcar, Gu Hang was led into a dimly lit meeting.... Once the chapter lands on I know we all have our connections, but who would complain about..., the chapter closes with I will definitely add an update tomorrow!
Chapter 174, "Closing The Cave", is the clearest early answer because it turns Damien's situation into a concrete plot event. It opens with The fifth tunnel loomed ahead, dark and unyielding. and closes on Before the demons took over." The realization weighed heavily on him..
Chapter 45, "Actively Hunting II", is the clearest early answer because it turns Damien's situation into a concrete plot event. The chapter turns that into something concrete by moving from As Fenrir sped through the forest, chased by dozens of Tree Demons,... to They were now both speeding toward him, hoping to arrive before the....
Chapter 420, "Terrifying Spiritual Energy, Tearing Through the Ship's Shield", is the clearest early answer because it turns Gu Hang's situation into a concrete plot event. The chapter turns that into something concrete by moving from This put him in a difficult position all of a sudden. to Even with the three cruisers focusing fire, there was no way the....
Chapter 457, ", Are You Signing or Not?", is the clearest early answer because it turns Wu Yang's situation into a concrete plot event. The chapter turns that into something concrete by moving from However, even Flying Wing Star, including the previously relatively... to How could that possibly be bad?" Ulrich heaved a long sigh and said,....
Chapter 445, ", Sect of Mechanics Can't Hold Up", is the clearest early answer because it turns Protection Army's situation into a concrete plot event. Early on, It might sound rather unkind, but in reality, preserving a fleet.... By the end, Under this premise, they did not want a core world like Jindi Star,....
Chapter 474, ", Let me show you the corpse", is the clearest early answer because it turns Titus's situation into a concrete plot event. It opens with Titus encountered his first deadly problem, and it was not human... and closes on Losing one, two, three battles — okay, no problem, as Mr..
Chapter 901, "chapters, the game is deadly", is the clearest early answer because the violence around Gu Hang becomes final instead of hypothetical. Early on, Today, Gu Hang is fully dressed in marshal's attire.. By the end, If one day the Empire withdrew Gu Hang's marshal position, it would....
Chapter 499, ", I Have Returned", is the clearest early answer because it pushes Space Domain Government into a new phase or setting. A useful checkpoint is the way the scene starts with The path to the Alliance was actually quite singular. and follows through with No matter how well-prepared, it was all meaningless..