You mean those books that the RCC didn’t officially recognize as canon until the Council of Trent.
I’m wondering what’s in them that Catholics think is so necessary for salvation that the Bible can’t do without them.
Praying to saints, indulgences, and purgatory for starters. Oh, and then there is the burning of fish hearts from which the smoke drives away demons. And also smearing of fish innards on eyes that have cataracts to heal them. Of course there is also the fact that having daughters is a disgrace.