Hand of Fate. Part 1: On the March

P.S.: Somewhere in the middle of the map, on the surface, Liches guard a hundred archers; you can take them (the archers) without a fight. I think this is an oversight.

But why are they guarded then? ;)
Answer: so you can take them and add them to your army. If you pay attention, there are at least ten different units on the map that you can recruit.