Celestial

Celestial is believed to be the language of the divine, and is used in older and more inaccessible religious texts and records. Most likely to be spoken and understood by members of the Clergy or religiously-inclined Academics, some of the Nobility also learn it as a status symbol.  

In Mythology

In some folk beliefs, angels are thought to speak Celestial, although such discourse is discouraged since belief in angels, while not a heresy, is viewed with caution.

Dictionary

10 Words.
Spoken by
Legality
Legal to know and use.