It would have been evidence of a caste structure, except that Diamond seemed inferior to Starlight, so it wasn’t just horn or wing that determined rank. That left the mark on their flank, the cutie mark, as the potentially determining factor, and he had no idea how that system might work. Undoubtedly, it was something like heraldry. Twilight might have a book that showed different marks, and even if he couldn’t understand the words in the book, it might prove helpful.