The Marvel Comics universe features various Earths. For example, Earth-616 is considered the main continuity, but there's also Earth-1610 and others. Each has its own set of characters and events that shape its distinct narrative.
One great 'Earth 616 Marvel Namor Graphic Novel' is 'Sub - Mariner: The Depths'. It really delves into Namor's complex character, exploring his relationship with the surface world and his own underwater kingdom. The art in it is also quite stunning, bringing the underwater landscapes and Namor's adventures to life.
The character development is a top aspect. Namor is a complex character, and these graphic novels do a great job of showing his growth and evolution. For example, his changing views on the surface world over time.
One aspect to consider in 'Crisis on Earth X' fanfiction could be the exploration of alternate versions of characters. Writers often take advantage of the multiverse concept in this storyline to create unique character arcs that deviate from the original canon.
The X-Men are part of the Marvel Comics lineup. They have their own unique place within the Marvel multiverse, with a dedicated fan base and a significant impact on the comic book world.