It’s just a bunch of fictional letters I smashed together in semi random order to make it look like a real language. I didn’t want to create a conlang, but I also did not want to write everything in English or French or whatever, since it is a minor plot point that the characters are not speaking a language of this world.
Some of the shapes of the letters are loosely based on braille, mostly by the idea that the letters should be easily recognisable by swiping your fingers on them, since the alphabet was meant originally to be used by an underground civilisation with limited access to light.