Nagobie

Slithering across the core of Rën, beneath the crust at the bottom of its mantle, you will find Nagobie, the snake without end. 
  In its earliest days after Braga created Rën, the life they had seeded there started taking hold. Braga gifted the world volcanic activity so that its lands would constantly renew.  They poured water upon it, intending for those waters to hold life within and provide for life without.  Plants, trees, animals, and fantastic beasts scoured Rën's surface, looking for shelter and the means of their survival. It was the survival of all their creations that troubled Braga the most. The God of creation didn't just hope for survival but wanted them to thrive. 
  Braga's earliest observations identified a flaw in their design. Rën lacked balance. Its creatures were stuck in perpetual day or night. They were restless and tired, and their existence seemed drudgery. The remedy was rotation; Rën had to constantly cycle from Light to darkness. This cycle would allow for growth, rest, and renewal.  With a purpose in mind, Braga imagined the largest creature ever created into existence and named it Nagobie.  Pleased with their efforts, Braga instructed Nagobie of its purpose, "Burrow through the dirt, sand, rock, and fire. Find your way to the deepest depths possible. There, you shall hold Rën in your coils, embracing it as you move across the depths". Nagobie did as instructed, and Rën began to rotate upon itself. Slowly, Light began to pierce the darkness, and darkness fell upon the Light. It is believed that when light and darkness meet, Nagobie's head passes its tail in the infinite loop of its coil, so the time between Light and dark is known as the passing.