Troll Enchantments

Nothing new is registered for the vanilla side. Every enchantment is the real one, with its real name, obtained the real way: enchanting table, librarians, chests, fishing. The only thing that changed is what it does. And the colour of its name in the tooltip: every rewired enchantment is a slightly different shade of grey (or red, for curses), so you can tell them apart once you know the trick. 

A villager that looks like a pillager (it never attacks, never despawns) and sells nothing but curses. One spawns next to every new Wandering Trader; there is also a spawn egg in the creative menu. Each book costs emeralds plus a book. These curses are not in the enchanting table: he is the only source.