Marvel has created enough characters over the decades that some of them barely survive a single story, a handbook entry, or the memory of one reader who refuses to let an extremely minor villain die twice. The Appendix to the Handbook of the Marvel Universe was built for exactly those people.
Visit the Naga entry in the Marvel Universe Appendix
The site is commonly known as MARVUNAPP. Jeff Christiansen launched the project in 2001, and it grew into a giant catalog of Marvel characters, places, races, alternate realities, and other material too obscure for ordinary reference books to handle comfortably.
By 2017 the Appendix celebrated its 10,000th entry.
That number explains the project better than any mission statement. MARVUNAPP was not trying to summarize Spider-Man for somebody who had never read a comic. It was trying to answer questions about the person who appeared in three panels in 1974 and was never mentioned again.
The master-list URL CacheRat found points to Naga, the ancient Lemurian ruler associated with the Serpent Crown and Namor mythology. It is a typical Appendix page: creator and appearance information, history, powers, relationships, clarifications, and references stitched together from scattered comics.
The larger importance is the structure around that page.
Before fandom wikis swallowed the search results
MARVUNAPP belongs to an earlier model of fan knowledge. A small group of deeply invested people chose a scope, developed conventions, researched primary material, argued over continuity, and published pages manually.
The result became influential enough that later Marvel databases, discussion forums, and comic researchers routinely cite it. Some contributors also crossed into official Marvel handbook work, blurring the line between fan reference and professional reference in an unusually productive way.
That does not mean every interpretation on the site is beyond dispute. Comic-book continuity is basically an industrial process for manufacturing edge cases. What matters is that the Appendix records its reasoning and points back toward appearances rather than flattening everything into a paragraph with no provenance.
Modern Web platforms are very good at making enormous databases. MARVUNAPP is interesting because people began building one before the obvious platform for it existed.
It grew because somebody kept asking, “Who was that guy?” and refused to accept “nobody remembers” as an answer.