Unequal Confrontation

My question was about the timing. I have dark magic maxed out (I have a berserker in one of the human castles, but no subjugation yet). I have inquisitors in my army – I need to bypass the castles, learn the spells, return to the first castle to strengthen my army with artifacts, and defeat the titans.
I apologize for repeating myself: at what point in the game did you fight the orcs?