Disclaimers: I wasn't part of the first closing round, and neither of the reopening ground. I haven't seen the edit history (before now), but I was one of those who voted to close it in the current stage.
I already commented on the question,
The power is quite general, I understand. As it stands, I don't think it would be unanswerable, so no IG (or it keeps on the right side) for me. However, you are asking about a specific use of that power... for a plot. So for me it is a plot building, and not world. The power is already there.
but I'll try to explain it further here.
I think it is an interesting question. I think it is answerable, so no idea generation, not too broad, etc. However, you present us with with a situation, and a power, as well as a typical use for it. Now the questions can be summarised as
How can my character use it in the best way to fool the others?
And to me, as interesting as it is, this is not about building a world. It is about developing the plot. And plot questions are off-topic.
Unfortunately, I don't think your question can be saved (to me), as the part of the world for that is already made. I really suggest you to join on the chat where such discussions can be adressed. And very welcome. Writers might be an option, but they also avoid discussing plots.