Necropolis discussions.

Actually, skeleton archers aren't that scary; goblins are noticeably stronger, so there's no need to be particularly afraid of them. In my opinion, the undead's dangerous units are vampires (especially in their upgraded form), liches in reasonable numbers (6 liches won't decide the battle), if those liches are even built... and the banshees; they are strong. In general, after playing undead in HotA and in single-player, one can say that the undead's strength lies in their cheap resurrection magic. Level 2 and 6 mana, and a quick clear of the map at the beginning, provides a good start. Their weaknesses are the generally low initiative of the army and the lack of clearly defined tanks in the undead army – monsters capable of absorbing mass damage.