Glorantha is, above all else, a world of myths. The gods are real, and their stories happen eternally. Mortals can venture into the Gods War to reenact their most formative myths. Such rituals risk harm to the clan and death for the quester, but can also work powerful magic.
Contradictory versions of a story can both be true, and hold magical power—but never interchangeable. For example, Riders and Wheels both know the story Hippogriff Reborn, but they tell it differently—and if they help their different-culture cousins perform the Gamari Horse Mother ritual that is based on it, they may find themselves in trouble: Wheels who help enact a version of the story hostile to Samnal's may lose his favor, while Riders who help the Wheel version of the rite may find Gamari herself insulted by their participation in a ritual that demeans female divine power.