I thought we were talking about planar binding and whether demons are hostile. Let's imagine that the DM has been very kind and you been allowed to pull this off. Let's imagine you have maintained anonymity and are allowed to boss them around with some form of telepathy.
There is now a voice appearing in their head telling them to do things. They're going to be hostile to the bossy voice.
He is claiming that his voice is i.m.p.e.r.c.e.p.t.i.b.l.e. The demons can't know the orders since they don't perceive them. Planar Binding adresses that "If the creature carries out your instructions completely before the spell ends, it travels to you to report this fact if you are on the same plane of existence. If you are on a different plane of existence, it returns to the place where you bound it and remains there until the spell ends."
Since no orders were given (as
@Hohige insists that he stays i.m.p.e.r.c.e.p.t.i.b.l.e including when giving order so the target doesn't know about the order given) they just stand around. They can't report anything since they don't know who bound them.
Which leads to this scene (with special thanks to Earth2Carnifex)
Hektula: "My Lady, our effort to free you have revealed a new thread of the Prophecy..."
Sul Khatesh: "Speak!"
Hektula: "The draconic prophecy states that you could be freed from the Couatls' chains by embracing voluntary servitude in the hand of the vilest creature ever, a lowly sorcerer".
Sul Khatesh: "I trust that you have immediately stopped investigating such a ludicrous chain of events, or should I appoint a new servant as my trusted prakhutu?"
Hektula
quickly signing out a death insurance: "actually there is some merit to it. You've been imprisoned for millenia... Serving a creature for a few month will be quick.
Sul Khatesh: "Have you identifed whom I am supposed to serve?"
Hektula: "Actually, yes. He's enroute to this place because we conspired to give him two itineraries leading him to your palace."
Sul Khatesh: "Two?"
Hektula: "The first lacked pictures. He threw it away as saying it's booooring".
Sul Khatesh: "You're not making a strong case for serving him, you know?"
Hektula: "We couldn't find a decent Sorcerer... According to Alfred, whose knowledge was consulted through Contact Other Plane, 83% of sorcerers die by their own doing."
Sul Khatesh: "And this one show promise?"
Hektula: "Yes, I commanded all our servants to ignore him and feign that their truesight doesn't work. He thinks nobody can see or hear him, because he was quiet and stealthy for a few minutes after his last long rest, three days ago."
Sul Khatesh: "I'll be his slave for 180 days you say? If that works I'll flay you slowly over 180 days."
Hektula: "Please, My Lady, it may be your quickest hope... He seems to be affected by incoherent hatred toward Wizard, he might ask you to kill them all. So you could just destroy the world as you wish to do, claiming wizards as collateral damage."
Sul Khatesh: "OK... Do we know why he's behaving like that?
Hektula: "No one knows. I tried to question the knowledge of the Abyss... The only story they told was of an interloper who visited Zuggtmoy, Orcus, Yeenoghu, Baphomet and Juiblex on a quest for vengeance..."
Sul Khatesh (taking the form of a giant question mark): "What happened?"
Hektula: "He didn't read the stat block until the end section about Regional Actions and fell pray to madnesses from all five of the lords, and rolled this:
| 01-20 | "My anger consumes me. I can't be reasoned with when my rage has been stoked." (Baphomet) |
| 81-00 | "My personality is irrelevant. I am defined by what I consume" (Juiblex) |
| 81-00 | "I keep trophies from the bodies I have slain, turning them into adornments." (Yeenoghu) |
| 01-20 | "I often become withdrawn and moody, dwelling on the insufferable state of life." (Orcus, referring to the Demiplane of Basements) |
| 41-60 | "I see an altered version of reality, with my mind convincing itself that things are true even in the face of overwhelming evidence to the contrary." |
| 61-80 | "My mind is slipping away, and my intelligence seems to wax and wane." (both from Zuggtmoy) |
[those are really from the tables Madness of XYZ in the stat blocks]
He has been roaming ever since, claiming to have successfully bound such powerful creatures. I advise that you just elect to fail your saving throw and follow an order of doom-spreading from this edgelord.
Sul Khatesh: "I agree, we'll do that. His pain will be eternal under my rule.
Hektula: "As you can see, he's here, "hidden" right behind the the spoon he's holding in his hand."
Sul Khatesh: "What does he do?"
Hektula: "he's casting spells that don't require a saving throw, hoping that you will use your Legendary Resistance."
Sul Khatesh: "I suppose we'll just ignore him..."
Hektula: "here, he's casting Wished Planar Binding!"
Sul Khatesh: "Moron, I FEEL EVERY SPELL AROUND ME, why do you think you need to inform me?"
Hektula: "Sorry My Lady, I needed to inform the audience that you were a real NPC with an actual backstory and not just a stat block."
Sorcerer:
mumbles unintelligibly
Sul Khathesh: "I FAIL MY SAVING THROW! AT LAST"
Sorcerer: "..."
Sul Khatesh: "I am free! My Couatl binding is broken! I will be ordered something that will make me leave this prison at last! My wrath will be terrible!
Sorcerer: "..."
Sul Khatesh: "Why doesn't he gives order to me?"
Hektula, using telepathy: "He thinks that giving imperceptible orders is smart."
Sul Khatesh: "You mean, he won't order me anything?"
Hektula: "He can't be this..."
Sorcerer
planeshifts away
Sul Khatesh: "That's not 180 days of flaying I'll inflict to you, that's 180 lifetimes."
Hektula: "I assess this is a reasonable sanction for my utmost failure, My Lady."
