Hmm... All forms of teleportation jammed, all entrances locked down, and it didn't seem like the walls would react to any form of assault. Together with what was going on outside it was safe to say that whoever had designed this had in fact been trying very hard to keep in account all possibilities and block them out. So... how would she bypass all of that?
She had received the letter, just like everyone else. She had felt the compulsion, just like everyone else. However the compulsion hadn't been complete: she couldn't deny the urge to attend, but she could still decide HOW she would attend. It only told her to come here, it didn't tell her how to come here or what she should do once here. Not complete enough to be enslavement, but too blatant to be a subtle trap. Someone who didn't have the power to do more wouldn't have done this much, and someone who could do more apparently could do enough that they didn't think leaving the guests with their independent thought would be an issue. Either an attempt at saving energy, or they wanted to see how people would react. Maybe it was actually a trap, or maybe it was just an extreme type of prank. It was hard to tell right now, as there was so little information available of the one who had sent the message, so one would have to attend the party to find out... If they even had the choice not to go in the first place.
The Regent of the Night. An ominous name, speaking of power and importance. The regent of all night, everywhere and always? Or was this a claim, a boast, speaking only of a small area or believing itself to be bigger than actuality. Once more not enough information available. Such lack of information was vexing, and would require remedy through constant observation. Regardless, this Regent and whoever was aiding her had the power to make so many people attend, and seemed to have done a good job shutting them all away, unable to leave or contact anyone who hadn't been able to attend or who hadn't been invited. No knowing who had been invited and who not, other than those who were actually present. Would have to ask others to investigate later, to see how many people had received an invitation but hadn't actually arrived here in time to be locked up with those who had attended. Was everyone who wasn't here simply unable to attend, or had there been people able to fight the compulsion? An important question which would require answering.
Regent of the Night. Addressed as female by her servant. Either misdirection, or an alternate title might be Queen of the Night. But Queen would imply the existence of a King, so maybe the term Regent was used to avoid making it sound like there was another, an opposite, an equal? An interesting theory, but once more the lack of information was making it hard to get a definite conclusion. The question here was whether the answer to these questions was important enough that the arrival of the Regent of the Night would be preferable over her staying away. For her to lock everyone present up like this her intentions were unlikely to be benign, and while those who attended weren't necessarily important to the careful observer said careful observer wouldn't want to be wiped from existence by a trap as simple as an enchanted letter. An embarrassing end it would be, and more importantly it would show a lack of strength, mental or otherwise. She had no choice in the matter as it was, but she would try her best to get out, and once she did she'd have to find precautions to make sure that future attempts to trap her like this would end in failure.
At least she had managed to enter the ballroom on her own terms. She had found someone she had met before, who was in possession of the letter. Silently she had joined that one, followed her into the ballroom like a shadow, so nobody would pay attention to her as they were all distracted by her unknowing companion. That way she could investigate in peace, without anyone bothering her... and even the most sensitive of sensors couldn't find her if the one she had chosen to follow was acting as a jammer, drowning out what faint signals she might still be sending out with her own noise. Once inside she could move more freely, as it became clear that many had attended, enough that the background noise should be sufficient to keep her hidden as she moved about.
Less tangible than a ghost, less visible than air, her presence non-existent as if swallowed by the void of time and even her very soul and magic as if never having been known, never having been sensed. She didn't like being found, so she would make certain that no-one could ever find her when she didn't want to be found. She knew of sight, she knew of hearing, she knew of touch, she knew of taste, she knew of scent, she knew of magic, she knew of soul, she knew of thoughts, feelings, emotions, intent, presence... She had done everything she could to find every single method one could think of with which they might be able to find her, and carefully eliminated every single one with training, knowledge, magic and trickery. Even gods weren't welcome to find her, at least so she hoped... The divine were tricky, information about them was often overblown yet also too small in perspective. If she could still be found she would have to find out how, and eliminate it... either the method by which she was found, or the person who managed to find her that way.
But for now, more importance was in discovering what situation she had ended up in, in all her care and paranoia. All her precautions defeated by a letter which had found her, which had breached her defences the moment she laid eyes on it. Whoever had sent that letter was dangerous, and she'd have to see if it was something she could eliminate as she was right now.
It was fortunate that the Regent appeared to have a liking for the dramatic and the mystique: flickering flames helped cast a lot of shadows, covering everything like slithering snakes and crawling cruelties, allowing her to freely move around without having to rely on lesser forms of stealth, without needing to hide behind the one who had acted as her entrance into this place. The people present, they were all talking, discussing, arguing, partying. Doing things people always did once they gathered. Some of them were wary of the situation, others weren't. One in a corner, looking at everyone else without partaking. Was she taking the situation seriously, or was she like the careful observer, disliking large gatherings such as these? Unimportant, but still a small question which could be answered easily in the midst of all of this.
The walls, the doors, the windows, they all gave the appearance of being made of normal materials. Wood, stone, metal, glass, everything that mortals already knew and could use. A good disguise, because the Regent most likely wasn't a mortal. The methods used to seal them off were grand, mysterious, they seemed to be outside of anything that even the most powerful known mages were capable of. And no mortal, no matter how strong they were, could ever claim to be the ruler of all the night. That would be nothing more than arrogance, pride, folly, and she would help them realize that if only so she wouldn't have to hear such preposterous claims any longer. But there was still the question of what kind of methods were used to lock them away. Beyond the walls, windows and doors the impression was given of an alternate place, one of darkness and dreadful shapes. But was it a reality, or an illusion? To be moved to an unknown realm would explain the inability to escape through any means, if the Regent was indeed not a mortal, and could control who could enter and leave the realm. A pocket dimension, possibly, where the Regent decided who could get in or out. But that the ballroom couldn't be destroyed, that the servant couldn't be harmed... That was beyond just a pocket dimension. It suggested a more tricksome power, something which she would have trouble dealing with unless she solved the puzzle.
If this was an illusion it would explain why they couldn't damage the ballroom, why the host was beyond retaliation. But how would they have wandered into an illusion? Was the letter not a letter of compulsion, but a letter enchanted carefully with an illusion of the highest level, making them all believe that they had arrived here? Such thing would be beyond mortal hands also, unless the whole spiel about the Regent of the Night was false to begin with, and this was a cabal, a group, working together to produce effects beyond that of a single mortal. It was a distinct possibility, something to keep in mind, but for now she'd just have to create theories, think of how to prove and falsify them, and keep them all in mind as she observed. For now there was little she could do but wait, and see what the people who had been trapped here with her would do.
Jiyu would hear a whispering in her ear, so faint that for a normal human it wouldn't have been audible, even though the whisper originated from right next to her ear. There was nothing tangible there, nothing with shape, form, presence, or anything else, but yet there was that voice, faint enough to feel like it wasn't real... but yet it was there, if Jiyu chose to listen, if she chose to accept it as real and take heed, even if she wouldn't have any sign of who had said it, what their allegiance was, what they were planning, what they might be.
"I advise care... The Regent most likely isn't mortal... And while we can't break the ballroom from within, whatever is outside might."
One person warned should be the same as everyone warned. Jiyu, the one she had used to smuggle herself inside unseen, was surrounded by people, so if Jiyu put enough value into the warning she would spread it. From mouth to ear to mouth to ear. To the careful observer those trapped with her had little inherent value, but their presence and their abilities might become useful... Especially if the Regent turned out to be as malignant as the observer had reason to believe her to be.