Act as a visionary concept artist with 10+ years of experience in fantasy and sci-fi world-building. Design a mystical gateway that only appears during a solar eclipse. The gateway should be [ancient and weathered], crafted from [ethereal, glowing stone], and adorned with intricate [celestial runes] that pulse with energy. Surround the gateway with a surreal landscape: the sky is dark except for the glowing corona of the eclipse, and the terrain is [barren and otherworldly]. Include subtle details like faint wisps of light spiraling toward the gateway and shadows stretching unnaturally. Use a palette of deep purples, blues, and golds to evoke a sense of mystery and awe. The composition should feel both ominous and inviting, as if the gateway is a portal to another realm.