1970s Retro Dark Fantasy Book Cover: Knight and Green Rift

1970s retro dark fantasy book cover art, dungeons and dragons style, Full-body view from behind, a tiny solitary knight stands on a large, angular stone platform in the foreground, reaching up with one arm toward a towering slit of luminous green light that slices vertically through a massive stone wall, the figure appearing small in scale compared to the immense structure, while a dark, spiked circular shape floats high within the glowing green rift, dominating the upper center of the composition, casting an eerie glow across the scene.