Alchemical symbols arranged with alphabetical correspondences. This is available as a free True Font download for your PC at dafont.com. The font is called Agathodaimon - type that in the search box at the site, Another excellent set of characters for secret writing in a Book of Shadows.
Pinning mostly because it looks cool. This anime series from the early eighties concerned first contact between humans and the Zentradi, giant humanoids created eons ago by a mysterious protoculture to serve as their galactic warriors. The series's creators, Studio Nue, constructed a Zentradi alphabet for the TV series, which they then supplemented with a full-fledged Zentradi language for the followup movie.
A Con Lang (or just "conlang") is short for "constructed language", e.g. a language the writer, their friend, or some other associate has made up for the purpose of using in a book or show. No, they did not just say that the Alien/Elf/Bee People speak a different language, they actually made up an exact vocabulary and grammar, one that can be translated into English (or equivalent). This is where Translator Microbes are abandoned and a dictionary given to the reader.