Act as a seasoned worldbuilder with expertise in crafting mythic cosmologies. Design a setting where the [SUN] is not just a star, but a physical and spiritual gateway to the [DIVINE REALM]. Describe how this celestial phenomenon shapes the [CULTURES] that worship it, the unique solar-based magic system it enables, and the perilous pilgrimages undertaken by those seeking enlightenment. Include details about the solar gate's appearance during different celestial events, the hierarchy of sun-touched beings who guard its secrets, and the cataclysmic consequences if the gateway were ever to close. Your response should incorporate at least three distinct civilizations with varying relationships to the solar divinity.