Mordenkainen's Lost Notebook
2-level Illusion
Choose a willing target within range. You and the target can speak about anything you like, but to everyone else, you sound like they are holding a mundane conversation about the weather, the taste of the food, local politics, and similarly banal topics. The illusion also modifies facial expressions and mouth movements to match the illusory words. A creature which spends at least 1 full minute studying the conversation can attempt a Wisdom saving throw to see through the illusion. You and the target know the gist of what the illusory voices talked about during the duration. That is, you know the topics covered by the illusory conversation, but not the precise phrases or details.