This world is actually a BinaryStarSystem. There are two suns, and Bardel travels between them in a figure eight pattern. In even years, the planet orbits a stronger sun, and in odd years it orbits a smaller, weaker sun.
The DarkDay is a very short period where the planet is making its transition from one sun to another, and neither sun gives light enough to be considered true daylight. The gods themselves erect a protective shield around the planet so that it survives that short transition.
There are other planets in the system as well -- great gas planets that orbit both suns as a great oval. There are also the remains of planets that died in some great cataclysm, likely in this system's formation.
This system is by its very nature chaotic, and comets and meteors periodically crash into the planets. If a large enough object did hit Bardel, it could alter the planet's trajectory and either send it into orbit around one sun, or send it careening off into the vacuum of space -- or into one of the suns.
It is rumored that a large comet, seen once a century, is on a course that would cause it to strike Bardel. This is projected to happen some time in the next ten years.