how to defeat the orcs? (Etherlords 2)

in the third chapter for vital, near the city there is an orc (they kill some hero) then attacks me. I don’t understand how to win, I spent a dozen battles ...
every move he summons the orcs, and with each orc their life and strength grows .. his cards never run out .. 10 fighters are always ready 11/9 ..
you just don't have time nothing to do, he's already gathering a crowd ..
medium difficulty.
I once played for a long time, I went through this map, but I don’t remember: maybe I missed this orc