Playing with zombie mode, if I'm lucky the city state that lets you choose your prophet's ability is in the game (Laventa? I forget which one). I pick convert barb's. then I park the prophet until I'm about to get overrun by zombies, then I pop the prophet into the middle of a zombie cluster. Instant zombie army. If I'm lucky, my prophet will have extra charges to use. Later in the game I combine zombies into armies, at least that way I can protect my cities. By that point all of the AI's are usually down to just a capital city surrounded by zombies. I slip a prophet into the zombies next to the ai city, pop them into my soldiers, take ai city in one turn as the zombies will have already took out the walls.