Dark Wizard army
The Dark Lords are powerful Dark Wizards that fought Four Hundred years ago against the Magic Council but were sealed away, it is implied their magic is somehow related to Dragon Slayer magic and that they knew both Zeref and Acnologia, however they do not confirm this analysis nor do they share anything regarding their allegiances or goals.
They do seem to have an interest in a trinity, specifically the destinies of Natsu Dragneel, Zeref and Acnologia as they themselves work towards an unknown goal.
- The Dark Lord each specialize in different field of Magic, it is implied they may be Dragon Slayers however they neither confirm nor deny the fact. They are so old and powerful that they consider the techniques of modern Wizards as immature and pathetic, compared to the strength of their fellow ancients. A similarity they have to Zeref, is that they do not announce their attacks before they use them.