Hiya, sorry for the random question. I have fallen back into this pairing and my mind remembers some fanfics from ages ago involving Glaive Noctis and another involving Braids. However my searches lead to very little or deatcivated tumblr accounts. Have these been wiped from the internet or do you know where one might still be able to access these?
The best advice I can give is to go to A03 and look though the nyxnoct tag there: https://archiveofourown.org/tags/Noctis%20Lucis%20Caelum*s*Nyx%20Ulric/works
There are still many wonderful writers that are active in this tag. Though, I do know a few writers who did do a lot in the tag are gone now, and I think one or two pulled down their stories as well. So, if they were the writer you're looking for it might be hard to find their stories. I'm sorry, I wish I could help more.