Shadow Rangers

In the land of Varga, peace has reigned for the past few decades thanks to the Shadow Rangers. A group of elite warriors tasked with defending the land from the forces of the Darkness that constantly seek to take over. Lately though the Shadow Rangers have had trouble pushing back the Darkness. As the Rangers worry about the encroaching Darkness, a young girl seeks to join the Rangers. The Darkness though will stop at nothing to stop her though from joining. How does she tie into the struggle between the Rangers and the Darkness? Is she the one who will help defeat the Darkness for good?