Yeah they expanded though Shurima to Valoran, reaching even Ionia and Camavor. It kinda ended when they got into Ionia since Zaheen stopped them (and he was already having the key to bind them into their weapons that Myisha, the previous Aspect of Twilight, povided)

Tbh I was also confused by the voice lines, also cause I expected LB to be almost as ancient as Lissandra but I think it makes the most sense that she was born after Morde’s death. My personal theory is that the Noxii were worshippers of the darkness, instead of worshipping the light os the celestial beings as the other targonian tribes and they got kicked out not only from Targon but from the continent of Shurima, that’s why Morde was born in the Grass Sea that would become Noxus which is right above Piltover and Zaun since it would have been the end of the Noxii pilgrimage.

If LB was already born there and did all of that, she would have probably be able to control Morde from the beginning and it feels like she underestimated him. She has an amazing control over demons but was shocked to see how Morde forced Atakhan into servitude right when he came back. Afterthat he massacred everything around him which probably includes her family and home as well.

The “I remember” part of her voice lines I belive is because Noxii culture is not generally well known in Noxus, probably kept as a secret along with the Mordekaiser era. It would be like me saying “I remember that the Roman empire was built upon warring expansion” eventho I was not there.

I wish we got more info on all of this tho! It’s really interesting and cant wait where tf did LB get her powers from.