Digital libraries that host "taboo" literature—books that were historically banned by governments or religious institutions (like the real-life Index Librorum Prohibitorum established by the Catholic Church). The Real-Life History: Index Librorum Prohibitorum
To make sure I’m giving you exactly what you need, I’ve broken down the most likely interpretations of this keyword. 1. The Pop Culture Phenomenon: A Certain Magical Index index of taboo
It’s one of the best-selling light novel series of all time, spawning multiple anime seasons and the incredibly popular spin-off, A Certain Scientific Railgun . 2. The Sociological Perspective: Mapping Human "No-Gos" index of taboo