When Darkness Falls — Liz Kreger

When the world descended into disease-driven chaos a thousand years ago, survivors had to choose which deity to serve. Riona Northstar elected to follow The Lady. After hundreds of years of service, restoring the planet to a balance with nature, Riona is weary and ready to rest. However, a seemingly chance meeting with a young girl could lead to her most difficult task yet. The Lady's brother, the Dark Lord, is restless and grows weary of waiting for his turn to rule. He intends to wrest power from The Lady and plunge the world back into darkness. Riona will need all her centuries of experience, plus the help of a mysterious wizard named Finnegan, to unravel the Dark Lord's plans and figure out how the young girl holds the key to saving the world.