[Baalz]

Yeah, when the hoards get to really absurd sizes your only option is battlefield wide effects. A lot of the undead counters (solar rays, banishment, dust to dust, cleansing waters, holy pyre, etc) will work when you're merely extremely outnumbered, (put boots of quickness on people with flabeaus or herald lances for instance) but LA Ermor does get to a point where you really have to deal with them as a homogeneous army rather than a set of units. Solar brilliance, earth quake, rain of stones, acid rain, etc. is what you want to be thinking about by that time, depending on your capabilities.