Massive Chalice

An immortal ruler is charged with defending their kingdom against the Cadence, a monstrous invading force whose very touch is lethal and whose passage leaves magical corruption behind. Guided by the sentient artifact known as the Massive Chalice, the ruler learns the Chalice needs three centuries to gather the power required to cleanse the land, and cannot leave the palace to fight. Instead they must dispatch attuned heroes into battle and, across the long generations, arrange marriages and bloodlines so that new champions are born to carry on the war until the Chalice is ready.