Bugged Main Quest

[LightMatter369]

So I'm reaching the end of the game and finished off all the cultists with the exception of Rhexenor The Hand from the delian league, now I only have to encounter Deimos in Pylos, Here's the issue, I still have to finish upgrading my spear but the last cultist I need is apparently only available through the main quests, however I do not remember ever coming across the quest for aristophanes that unlocks this particular cultist (Rhexenor The Hand) I took about a 2 month break from AC:Odyssey but I see no reason why I shouldn't be able to do the quest regardless of where I am in the story. I looked up the issue on the internet and many others have had the same problem, I see no solution to this other than finishing this NG and doing NG+ and focusing only on doing main quests. If I ever did do the play quest that unlocks the cultist, there should be no reason why I shouldn't be able to kill him now.

I'm currently lvl 71 and should of course have all cultists killed except for Rhexenor, again I would truly appreciate any ideas that may help me with this, or maybe the quest is just outright broken for many.