The Great Consumption

The End of All That Was began with the Great Consumption, as the god now known as the Devouring Heart learned the secret of usurping the powers of other gods. First in secret, then with unstoppable power, the Heart began to consume the other gods of Khalaan. It took their aspects into itself and with every divine victim, it grew stronger and stranger. In its victory, it became the first victim of the Scramble; as it digested dead gods, it changed and mutated. As its domain expanded within its roiling gut and slavering maw, those begun to change too. Not even concepts or ideals were safe from the great change - things divided by divinity were now brought together in a melted slurry.
Small were the gods first consumed, and small were the changes wrought. Animals and plants began to be one and the same; wolves laid seeds to grow new pups, and trees walked on all four like great beasts. Fish swam in the skies, birds soared beneath the ocean waves, unhindered by water. At first, each change was a stumbling step across a generation, but a glutton never slows the feast.
The more that it ate, the more the heart wanted. Its power grew, and so did the size and glory of its victim. The gods of elf and orc, man and beast, sun and moon all fell, one by one and then by greater numbers. By the time the pantheons had stirred themselves to action, it was not yet too late. Some tried to fight, but always parted by faction and philosophy. Good would not help evil, ancient grudges kept allies as enemies. Others saw the event not as an inevitable demise, but as opportunity. Old, divine scores could be settled in the chaos, murder blamed on the Great Consumption.
Instead of a killing blow, they delivered themselves to the Devouring Heart piecemeal, as if part of a banquet. Changes that had once spanned decades now came in months, weeks, and days.
It ate, and ate, and ate, until there was were no more gods great enough to sate its hunger. It began to eat time and space, finally consuming the limits of the world and opening Khalaan's everwilds to grow beyond all boundries. With that last morsel, the Devouring Heart realized it had become too vast. To keep itself from consuming the world, then the stars, and all that ever is, the Devouring Heart turned its hunger inwards and fell into a deep slumber - perpetually gnawing on itself to save the world from its appetites.
No matter how great its hunger, the Devouring Heart is never known to have consumed mortals. Either as pity and compassion, as the Cult of the Hungry would have you believe, or because we have no nourishment to someone who wants to consume the very stars if you ask the cynic.