There are different types. Just like we have units with better equipment (weapon/armour)
Overlord just disappeared from Fengen. A late christmas gift from Tom?!
Ones in Ketampkin are very strong cavalries while those units led by Nightfall of the East are generally weak archers.
Once you defeat the powerful versions of each type, they seem to recruit weaker. CS wise they are similar.
But when Nightfall of the East attacked Enweil with 8k for the first time, he was leading really good archers. Not the second time however. The second time, he got smashed and he had a weaker version of the previous archers.
