Ancient Tongue of the Wise
The Ancient Tongue of the Wise is an a priori fictional conlang which was created by Mike Singleton in 1995. The language has only a brief grammatical sketch and a handful of words and phrases. It was used in a videogame series, Lords of Midnight, and in-world is used as the language of magic-casting.
The language was heavily influenced by Tolkienian languages.
Some examples of the language and a short grammatical breakdown can be found here.