Play the Yellow Turban level, on the Han side. You must defeat Zhang Bao and Zhang Liang, in that order, without any gates being lost. Once you have done this, a supply team will appear on the northwest enemy entry point and will make its way to the entry point on the top center of the screen. Kill the supply captain to get the Cao Cao's fourth weapon, Wrath Of Heaven. This weapon is well worth the work. His sixth attack has a purple haze around it and will kill anyone on contact except a Boss.