Final answer:
The most apparent feature of epic poetry in the given line is the grandeur of style, which is reflected in the majestic imagery used to describe a gem-bedecked palace at night.
Step-by-step explanation:
The feature of epic poetry that is most apparent in the line "Gem-bedecked palace, || when night-shades had fallen" is grandeur of style. Epic poetry is characterized by lofty language that describes majestic and grand settings or events, often to invoke a sense of awe. The line specifically highlights a grand setting with the use of vivid imagery, making the palace not only opulent but mystical as it's associated with the onset of night.