Kaelum is a dark fantasy medieval world in three great regions: The Woods, The Misty Lands and the Frozen Mountains. For most of the game the Moon-Knight walks through it on their own. Loneliness is an important part of the story, as the player will walk through ruins, ancient temples,castles, fortresses and swamps and will explore them on their own. It contrasts with a fast close combatwith knights, banshees, ghosts, goblins and wizards.
They wake from a coma on Centralis, a lake island in the middle of the continent, and meet Death, a strange figure who promises to revive them every time they die. The island is the prologue, the three acts begin when they leave Centralis. The task is to restore the Moon Goddess by recovering the three fragments.
Each fragment is at the end of a fantastic set world: the Crescent in The Woods behind the Wizard-Knight, the Half-Moon in the Misty Lands behind the Centaur-Knight and the Full Moon in the Frozen Mountains behind the Sun-Knight himself. At the Misty Lands fortress the Moon-Knight is attacked under siege, captured and sent to the north. Escaping that captivity opens the last act.
The Sun-Knight was the Moon-Knight's partner, back when the Sun and the Moon worked together. He was the first to see the Gods of the Gaps fallacy for what it is: the Power of the Gods is a manipulation of quantum states, not divinity and Kaelum built its faith in the gap. What he saw in the moon was dark enough that he broke it apart and hid the pieces. When the Moon-Knight discovered it, they faced each other and the Moon-Knight got sent into a coma.
Throughout the game the player learns why Death was so generous. The Moon-Knight was returned because of unfinished business and when it is finished they go back. On the highest mountain of Kaelum the player decides whether the Gods of the Gaps fallacy ends there or stands. Either way the Moon-Knight dies, this time hugging Death, and welcoming it at last.