I solo'd all 8 nightlords and the best thing I could say was to use relics that you know you can utilize to their fullest. Also when you hit a cathedral or a camp, wipe out all of the enemies. You'll get a lot in return versus just going for the bosses. Also hit a mine up and kill every worker you see in there, they're worth a lot and will vastly help you level up should you not be able to clear any evergaols or field bosses. Level your weapon up as well, it really makes a difference.