The Cult Unmasked achievement in AC Odyssey

Really useful guide, just thought I'd comment some of the issues I had along the way in case anyone had the same;
1: Podarkes the Cruel, I did not have the side mission 'Rebel' as I had not completed the side quest 'Trouble in Paradise', which is kind of like a "primary" side quests, primary in the sense that it is with Barnabas. Podarkes was revealed to me as a cultist during 'Trouble in Paradise' and he was also the region Leader. Previous to completing this side mission there was no region Leader.
2: Melanthos, from the research I did, you need two clues to be able to unveil him and track him on the map. I couldn't find how to get the second clue. I only had one and could not track him. IGN's walkthrough is correct however. And you can find him without getting the second clue. I looked up a tutorial to see what his ship looked like and then I was able to find is in the sea just west of Messara. It didn't notify me that he was a cultist until I had killed him though.
Hope this helps anyone stuck like me.I haven't killed all of the cultists yet but after sparing Lagos he shows as killed the same way all of the other cultists did (red icon and their back turned in the detail screen) it also awarded me his triangle piece, after I completed the quest (not immediately after sparing him).

I think this is why the achievement is to "Defeat" them not to "Kill" them. Technically I defeated Lagos with words.

It should be noted that in order to convince Lagos to leave the cult and spare him, you can't kill the Monger in public. You have to help Brasidas kill the Monger silently. If you don't, you lock yourself out of being able to spare Lagos and regardless of what you choose at the when confronting Lagos you are forced to kill him.