In the Before Times, there were no people. The gods created puppets, placing their pieces on the board of the world and playing the game of moving them across it as their fancies took them.
Fate was the strongest of these players; whatever Fate ruled became true in the game. Some of the gods grew bored with the game and found other pursuits; some kept playing, enjoying the stories they told and inventing puppets from whimsical to horrific. One of them placed two pieces on the board, twin children named Lixas and Luxas, but quickly tired of them and the two ceased to move through the world.
Lixas said to Luxas, "what should we do?" Luxas thought about it, withdrawing into meditation, neither eating nor speaking until they found the answer. A year later, Luxas replied, "we shall do what we will." They two of them set off on their journey, pushing other pieces off the board, upsetting carefully planned strategies and moving turns out of order. Finally they came face to face with Fate itself.
Fate looked at the errant pieces and moved to sweep them off the board, but looked into the eyes of Luxas and found it could not. Lixas drew their weapon and slew Fate, declaring that there would be no more puppets or pieces, or games played by far-away gods, only people like themselves who would determine their own fates. Their children became the thousand peoples of the world, unbound by Fate and burdened with the responsibility that Fate once bore.
The legend of Lixas and Luxas exists in every culture found so far; the race and gender of the twins varies from telling to telling, and the names may change slightly, but the core of the story remains the same. Sometimes they're associated with the sun and moon, sometimes mountain ranges, occasionally weather phenomena or local landmarks. Most often though, they seem to be a boy and a girl of whatever lineage is telling the story.
It's rare for legends to explain the absence of a god; there's certainly no story that explains the lack of a god of cake or ants, but it's also true that there are multiple gods claiming dominion over most concepts that have been thought of.
It's also clear that while cults of Fate arise wherever there is strife or hardship, none have been successful. Their clerics receive no divine powers, their prayers and entreaties remain unanswered, and any miracles attributed to Fate can just as easily be explained by Luck. Clearly some explanation is needed for why every other worship is rewarded; perhaps the story is a warning to those who would waste their time wishing for the world to be other than it is.