Which language is spoken in the inscription on J.R.R. Tolkien’s One Ring?

The inscription on J.R.R. Tolkien’s One Ring is written in the Black Speech of Mordor.

The words are the opening lines of a longer spell: “One Ring to rule them all, One Ring to find them, One Ring to bring them all and in the darkness bind them.” The inscription appears when the Ring is heated, revealing fiery letters on its normally plain surface.

Tolkien created the Black Speech for Sauron and the servants of Mordor. It is not the same as Quenya or Sindarin, the major Elvish languages, and it is not Khuzdul, the secret language of the Dwarves. The lettering is generally represented with Tengwar characters, but the language itself is the Black Speech.