Knowledge is Power

As much as Random enjoyed seeing Crimson humiliated at this command, he also had needs, during class he couldn´t stop thinking about what he should do next and wondering how else he should use this power over her, of course, he took care to mentally block his thoughts from her, some things are left best for her imagination.

First things first, he needs to know more about Crimson and her powers, so he starts inquiring her mentally, "Tell me, do you have any illusion or hypnosis spells we could use?" She looked at him, her desk beside his own, she answers "Yes, I am a succubus, it would be weird if I didn´t know any such spells, don't you think?" Again with the snarkiness though, for now, he let it slide as he says "Which ones?", he knew she was compelled to respond truthfully:

"I can make us invisible to anyone, but they would still be able to hear us; I also have a spell to make anyone here see but not really notice us, but it wouldn´t work with touching them, as I can imagine how would you use such power; I don't have a hypnosis spell, but I can make simples suggestions to the mind of someone who´s relatively weak-willed to make them follow simples instructions, but nothing complex."

Random pondered about it for a while, "What is the range of the spell for making us go unnoticed?" She thought for a second and says "This whole classroom, so, about 20 meters radius around me." Random smiled, it was a pretty useful thing to know, but he needed to know more: "And how about duration? Do you have to use some sort of 'magical supply' to use such spells?", she responds promptly, now feigning to study the textbook:

"Yes, I have something analogous to mana, my demonic energies, of course, they are limited, say I used that spell for its maximum range, I could maintain it for about 30 minutes, but if I halve the spell range, then the 'mana' consumption would be halved as well, meaning I could maintain it for 60 minutes, and so on, of course, I could halve it indefinitely, but I'm pretty sure you don't care about atoms seeing I give you a blowjob. Also, the number of people around the range would also affect its mana consumptions, the previously stated duration was for a single person, each person would halve the duration of the spell."

That was interesting because he could enforce truthfulness in her, Random was learning more and more about how her powers worked, now, his only limitation was his own creativity. He had more questions though, so he sat with him right beside him and said, again:

"Say you use this spell outdoors, what would anyone outside the radius of the spell see, if anything?"

"They would obviously 'notice' us and act accordingly and worse, once this is the case, the spell will no longer work on that person unless I recast it, which would affect mana consumption."

"So if someone enters the library while the spell is under effect, but they didn´t notice us before entering the spell range, would it still work?"

Crimson thought for a moment, not thinking about a lie, obviously, as she cannot lie to him, but the question seems to have perplexed her as if she never thought of the possibility:

"Yes, I think they would, but I never tested this scenario, you´re surprisingly smart, aren´t you? Anyway, think of the spell as a button you have to push, I can push multiple of them at once, but every new person would require another 'push', so yes, I do believe even if they didn´t notice us previously, they would certainly do so after seeing us."

"And what happens if you 'push' this button after seeing us, do they forget they did or would they believe they are hallucinating?"

"Neither, the spell does not affect the mind any further, but imagine they see me giving you a blowjob in the middle of the library and then suddenly, after an instant, they can no longer do so, in the lack of any logical explanation to this event, it would be reasonable to assume such a person would believe they are having a hallucination, how someone would react to that depends on their mental health, I would imagine, but none of those effects are directly caused by the spell, but are a consequence of its effects."

The bell rings, before he could inquire her further, announcing the end of the period, he and his pet demon begin walking through the corridors, he, of course, makes her follow him, and finally, they reach their destination: the library.