The final chapter in the Path of the King is the Black Gate where you'll do a lot of fighting, concluding with a battle with the Nazgul.
Kill the Orcs, avoid getting captured by the Nazgul, run up the stairs, climb down the ladder and take out the archers.
Of course, she doesn't find it, and it is her battle with the Nazgul king that helps turn the tide against the armies of Mordor.
The nine kings who wore their rings of power became the Nazgul, the shadow riders and completely subservient to Sauron.
The Nazgul were sent to find the One Ring, which was now in the possession of Bilbo's nephew Frodo.