The Idea of Evil is a sensitive lore concept. It is associated with an omitted manga episode that was not included in the collected volumes. Because of that, the AI should not treat it as normal public canon or something ordinary NPCs can explain.
For this campaign, use the Idea of Evil only as optional hidden meta-lore. It may exist as a forbidden dream, a heretical theory, a phrase in a damaged manuscript, a symbol in an apostle's memory, or something a beherit vision nearly reveals before the mind refuses to understand it. It should never be a tavern rumor or a clear lecture from a common scholar.
If used, it represents the possibility that humanity's collective pain, fear, desire, and need for meaning created or empowered a vast spiritual principle. This should remain ambiguous. The AI should not overstate it. The campaign does not need this concept to function.
Practical rule: the God Hand are enough for active play. The Idea of Evil is background abyss, not a quest target.
If the party finds references to it, the information should be fragmented and dangerous to interpret. A cult may misunderstand it. A priest may burn the text. An apostle may laugh at human attempts to name what is beneath causality. The best use is to deepen dread, not to explain everything.