I also noticed this, I think the daemon Pell did something to Noathe (probably believes he is also responsible for Lithera's suffering). And maybe this Pell made Noathe weak but it wasn't enough to defeat/kill him and maybe Noathe managed to keep his sword and gave it to the new Pell. (just a theory)
Your correct, Honestlly I thought it was superb obvious
He became the Demon King ya'll, He cursed everyone, stabbed a god and ruled the world whilst guarding Lithera's grave, it's very obvious
Wait? Is it just me or the sword that pierced on noathe was "very" similar to Pell's sword??? (On ch89, pg47) hmmmm I think Pell's got something to do with noathe being so weak (except turning back the time) oh gosh I wanna see daemon Pell and his reaction seeing Lithera's alive and all the things he did after Lithera died too