The Taboo skill is something that Shows when you do things you shouldnt do or learn/use skills you shouldnt use. Once you reach LVL10 of the skill the skill will finally activate and probably install "The Truth" about the World which lets People normally get mad or lose their sanity or changes their character though the Thing about it implanting the truth in you is just my guess because in chapter 198-200 you can see that Kumoko seems to know about the Robots and the Energy there but since it never showed when she learnt about it and the only Thing that is still unclear is the effects of Taboo i guessed that it is because of that