one of the demon lord's top intelligence figures, for example? Those who know for certain aren't new to spells and items such as what you're using.
If your character is that, then any individual who hears knows a the fact about Astiorth, plan and simple. The only reason they have for not taking your word for it is that you are a demon but there no point in really mistrust ingredients a demon pointing out another demon. Another thing is that only holy figures could detect his aura, by all accounts, you character is technically not holy. You are a mage, not a cleric, or a paladin, or a priestess. Also, while it depends on a personal view, demons are not holt either, that is why it is called demonic. But it is what it is.
My only goal was to use these items to set up a dynamic that would cause the group to look athrough each other in a new liget that almost forces them to actually look at each other as individuals and not as mere demons and humans, but now there is no point. As for the demon lord, all the was given is that he can talk through a host, it said nothing about his abilities being capable utilization through a mortal human body.
Again, I'm seeing these items as a waste of space and would have much had rather spent the time making items to benefit him in combat I stead of using trust to rely on his team to make up for his lack of versatility in a fight.
Since the human heard you, there is also no reason he wouldn't tell the others.