In the strange world of Terra, thousands of years have passed since a life-devouring corruption consumed the planet and everything on it. The Terran people take refuge under the Crystal Spires, mysterious obelisks with the power to not only repel, but purify the corruption. Those who inherit a Spire’s Heart, a small heart-shaped crystal embedded in the top of your hand that connects you to the Spire, are called Sentinels, and charged with protecting it from those who seek its destruction.