Why "He has returned"?

Was he the egg that Bard took away? If so, how did it managed to hatch? I picture Bard being a goofy-clumsy figure, (like the Precursor in Jak and Daxter), having dropped it by accident in lava or something. It'd go nicely with the Yin Yang theme, where the darkness (Aurelion) is born out of the light (Bard) but in a comic funny manner.

Anyways, why is he returning?

Are we hearing about the times when he was here before? Is he going to stay lore-wise? Or is he a boss to be fought and destroyed?

I mean, first, look at him. He's bigger than malphite I'm pretty sure, so just by stepping in Runeterra he can smash cities. Secondly, look at his powers. He crafts fireballs. Third, look at his name, Star forger. I don't know about you but the aspects don't seem up to it. Only Bard ofc.

I wonder if he wants or needs something from people (like worship) for not having destroyed them all already! And if he tries, Bard comes in - and if Bard comes in, what happens? Lore-wise this must be settled :|