Infernal

One of the Six Eternal Languages and the native tongue of both Hell and Abaddon, and the progenitor of Akadian and the many dialects spoken by Tieflings the Grimm. It is a language of strict rules characterized by precise elocution, designed to limit sloppiness and deny creativity. Infernal has two modes: sharp and conspiratorial, like a harsh whisper of condemnation; or commanding and stentorian, like an Urdan general. At once polished and cryptic, every tense is conditional but there is no subjunctive, making it the perfect language for contracts and judgment.
The written form is called the Infernal Script, which similarly exhibits oppressive codes and rules.