3. Welsh: Welsh is the first language I associated with fantasy books. Cooper's The Dark is Rising series, and Lloyd Alexander's Chronicles of Prydain both rely heavily on Welsh language and legend. My youngest daughter's name is even Welsh, and means "little raven." Good thing she has dark hair!
2. Russian: After attempting to read my dad's copy of War and Peace one summer, I was inspired to take Russian language in high school. That led to a Russian minor in college, and traveling to Russia twice. Russian is a Cyrillic language, and looks pretty, especially if you can master Russian cursive. Recent fantasy books such as The Crown's Game by Evelyn Skye and Leah Bardugo's The Grisha Trilogy use Russian, but sadly, most books will only use Russian phonetics. I am guessing it would be expensive and tricky to use the actual Cyrillic characters, but they would look more magical.
1. Elvish: Of course, a made-up language created by a brilliant linguist wins my top spot. J.R.R. Tolkien was not only an amazing author, but created an entire working language, with it's own characters, as well as grammar and syntax, along with several variations, for the land of Middle-earth. You can listen to the song "Lothlorien" and see the phonetic and Elvish translations, at this site. Or, you can listen to Tolkien recite a poem in Elvish here. Some day, when I have lots of free time, it would be fun to learn Elvish. . . or Welsh. . . or brush up on my Russian. Ah, free time. . .
|This Digiphile Wordpress site shows the first article of the Universal declaration of Human Rights, as well as lists several Elvish Translators|