I am about to coin the word 'conundrous' because I needed it (and I think it deserves a place in the dictionary)!
I would like comments on what you think about using 'conundrous' in the context of a serious article. But if you can supply one or more adjectives that are synonymous with 'conundrous', that would also be the answer for me. :)
If there are none, I will be happy to accept close synonyms (here's the definition of conundrum in the sense that I'd like to use it)
I'm after the "difficult problem" (but not the "pun") synonymity. It's used to describe a word from an ancient text which is seemingly not in the dictionaries; hard to find information about.
There's enigmatic, but it's just a mystery for the moment; it's not something that is by definition mysterious.
There's elusive, but I think that carries the connotation of something forever escaping one's reach.