Guhhh?

In my interpretation, Nightmare occasionally enters a state where the liquid corruption disappears and he returns to his white-bone form. Because of that, the gang already recognizes what his white-bone appearance looks like, so when they see the child version of Nightmare, they wouldn’t really question whether it’s him or not. Of course, he’s much smaller and completely unscarred compared to the version they know.

And well... I guess it’s finally time for me to talk about this part properly. You’re probably wondering why Killer reacts so strongly here. In my interpretation, Killer would react the worst to changes in Nightmare. He’s deeply obsessed with the boss’s permanence, so seeing him appear weak would shake him badly.

Killer experienced every single thing he once believed would last forever disappearing from his life. The love of his family, the friendship of the people around him, even the beliefs he once thought he would never abandon — he destroyed all of it with his own hands. Even the “human” who caused all of it eventually grew bored of him and left him behind as though tossing away a finished toy.

He thought at least the pain and loneliness would remain forever, but even that disappeared once his soul changed and left him emotionally numb. By the time Killer had completely given up and accepted that there was nothing left inside him anymore, Nightmare appeared after sensing his despair and took him away almost like some kind of “collectible.”

Killer assumed that wouldn’t last either, but Nightmare neither treated him kindly nor cruelly enough to destroy him. He simply kept him. They stayed together for an incredibly long time, and throughout all those years, Nightmare managed him with the exact same detached attitude without ever changing.

Nightmare never even treated Killer like a real person, but strangely enough, that was exactly why Killer came to understand that Nightmare would continue existing forever without even blinking, even if Killer himself disappeared. The fact that something truly permanent still existed in the world — something he could never destroy no matter what he did — gave him a strange sense of comfort.

Because of that, Killer hates seeing Nightmare change. Especially if he starts looking weak. Nightmare’s white-bone form makes him feel as though Nightmare is suddenly capable of ending someday, and Killer becomes terrified that he might somehow destroy the permanence he finally managed to find again.

That’s why a frightened Killer attacks Nightmare. He’s trying to calm himself down by proving that his attacks still can’t hurt him. And in reality, Nightmare truly cannot be harmed by him regardless of what form he’s in. So Nightmare usually just allows Killer to stab him until he calms down, because he knows that’s the fastest way to settle him.

But in this situation, child Nightmare absolutely can be hurt. Logically, that’s obvious, and Killer knows that too. But that fact itself heavily worsens his anxiety, and he spirals into a deeply unstable state. Killer is the type of person who survives by attaching himself to something. No matter how functional he may appear, he’s still damaged enough that once the pillar supporting him starts shaking, he collapses faster than anyone else.

So after realizing the situation, Killer becomes the least stable person there. Normally, Killer and Horror are the ones who handle judgment and leadership whenever Nightmare is absent, but because Killer is in that condition, Horror ends up taking full control of the situation alone.

The gang has a rule that they should never travel alone during combat situations — at minimum, they move in pairs. Usually, when they go out to spread negativity, the teams are Killer with Cross, and Horror with Dust. Killer and Horror are the ones who usually make decisions and give orders within their respective groups, but their judgment styles are almost complete opposites.

Killer tends to think in sudden, impulsive, flexible ways, while Horror is cautious and heavily survival-oriented. Because of that, Killer and Horror often disagree whenever they make decisions together, but ironically, that actually works in their favor. Both of them prioritize logic and efficiency, so instead of clashing emotionally, they tend to compensate for the blind spots in each other’s thinking and arrive at better conclusions together.

Cross usually receives orders from Killer, but unlike on the battlefield, Cross honestly doesn’t trust Killer very much in everyday life. Killer constantly pulls especially nasty pranks on him, and Cross’s personal trust in him is honestly close to nonexistent. (Though admittedly, that’s only half a joke.)

Because of that, Cross naturally relies on Horror whenever they’re inside the castle. Horror generally gets along well with everyone there. Even Killer doesn’t really play weird games with Horror, and instead acts as though he genuinely respects someone he regularly exchanges opinions and decisions with. Dust goes without saying. Horror is unquestionably the person Dust talks to the most — although even then, that probably still doesn’t exceed ten sentences a day.

To them, Nightmare’s transformation is essentially an emergency situation equivalent to the boss suddenly being absent. So they naturally fall into their assigned roles, recognize that something is wrong with Killer, and follow Horror’s lead.

Because Horror always prioritizes safety first, he understands that if Killer completely loses control, the only person capable of handling him without getting hurt is Nightmare himself. That’s why he decides to retreat to the safest place in the castle: the boss’s room. He knows perfectly well that if someone gets hurt while trying to handle things recklessly, Nightmare will be in an absolutely horrible mood once he returns.

Nightmare’s room is protected by ancient magic that even they cannot fully understand — something far older than ordinary monster magic. Nightmare allowed them access to the room in emergencies so they could use it as a shelter if they were ever endangered while he was away. He even told them how to activate the protective spell. (If you’re curious, it involves placing a very specific book marked with a magic circle into an empty slot on one particular bookshelf.)

So naturally, they all gather in Nightmare’s room and try to understand the situation and figure out how to handle it. Well... aside from the berserk Killer situation, anyway. But honestly, that problem will probably resolve itself once the boss comes back. Or after Killer exhausts himself and passes out.

Everything would obviously be incredibly confusing for child Nightmare, but at the very least, these strange monsters don’t seem like they intend to hurt him. Horror treats him surprisingly kindly, almost as though he’s personally interested in him. Cross awkwardly fumbles around like he has no idea how to interact with child boss, but still tries to smile at him anyway. Dust remains mostly indifferent, but continues prioritizing Nightmare’s safety whenever things become dangerous.

Honestly, they probably should be far more worried about the situation than they actually are, but all of them behave as though Nightmare’s return is inevitable and never even question it. Nightmare is deeply possessive toward the things he considers his. They understand that they themselves cannot escape him, but because of that, they also understand that Nightmare would sooner destroy them than abandon them. It’s less trust and more resignation, honestly, but it’s still stable in its own way.

As unstable as the situation may seem, the gang still has a very clear structure. They react quickly under pressure, rarely panic, and function almost like a properly trained organization. Cross, unfortunately, tends to suffer the most during situations like this, considering he’s comparatively newer, the most normal one there, and usually Killer’s designated victim... but well. Things are technically still under control.

So child Nightmare would probably manage to stay relatively safe until the problem resolves itself. The gang generally avoids asking him personal questions, so there would definitely be some emotional distance there, but probably not enough to make things actively uncomfortable.

Once Killer finally collapses and wakes back up again, he’ll probably become completely quiet and lock himself in his room. He doesn’t want to confront Nightmare’s humanity. It feels too personal, too fragile, too much like something capable of changing. So he’d avoid the situation as much as possible while trying desperately not to spiral again. That’s probably the best coping mechanism he has in a situation like this.

Cross, on the other hand, is intensely curious about Nightmare’s personal life. Tiny things, like what genres of books he likes, or how much sugar he puts into his coffee. Cross has a tendency to crave attachment, and he becomes curious not only about the boss’s private life, but about the others’ as well.

At one point, Cross complained that he didn’t understand why nobody else ever asked about those kinds of things.

Horror simply shrugged like he already knew the answers anyway.

Dust rolled his eyes like he couldn’t care less.

And Killer dismissed it with, “That’s private.”

When Cross muttered, “The boss already knows all of our private business anyway,” Killer just snorted and replied, “We don’t have privacy, Crossy.”

Cross looked startled by that, but he never corrected him either.

Most of the time, Cross avoids asking personal questions simply because he thinks it would be rude, but he’s honestly terrible at hiding how curious he is. So naturally, he becomes curious about child Nightmare’s preferences too — and whether any of those preferences still carried over into the current Nightmare.

Honestly, he might end up becoming the person who hears the most personal stories from child Nightmare. After all, even as a child, Nightmare could still read emotions. And unlike the adult Nightmare, child Nightmare wouldn’t simply ignore them.

Horror would probably treat Nightmare with the most natural familiarity. He’s actually the person who knows the most about Nightmare’s personal preferences. Most of it was learned through observation rather than direct conversation, but Horror isn’t the type to talk about those things openly anyway. He knows what kind of coffee Nightmare prefers during his white-bone state, what temperature he likes things served at, even what pens, ink, and parchment he usually prefers.

To Horror, Nightmare is something very close to a benefactor. During the time Horror was drowning in starvation, violence, and despair, Nightmare appeared after sensing his emotions and came simply to watch. Horror immediately recognized him as someone dangerous, but at the same time, he was utterly desperate. So he knelt before Nightmare and begged him to save his brother, promising he would do absolutely anything in return.

At the time, Nightmare’s castle only had Killer and Dust living there, and the two of them fought constantly like complete lunatics. Their personalities clashed horribly, and they projected their own personal histories onto each other so heavily that it turned into outright disgust. Nightmare became exhausted from constantly mediating them, so he eventually decided to bring Horror in to handle that role instead. If it didn’t work out, he could always just dispose of him afterward anyway.

But Horror ended up doing the job perfectly. Killer and Dust stopped fighting as often, and Horror voluntarily took over cleaning, organizing the castle, preparing meals, and handling countless small details the others ignored. He paid attention to things nobody else cared about, and Nightmare decided he was useful.

In return, Horror was given enough compensation to feed his brother properly and still have plenty left over. He follows Nightmare because he genuinely considers him the person who accepted him and saved his brother’s life. Because of that, Horror has the most openly human concern for Nightmare and constantly tries to look after him in subtle ways. Naturally, that would extend to child Nightmare too. He would almost certainly become the person child Nightmare feels the safest around inside the castle.

Dust, meanwhile, is uninterested in everyone equally — including child Nightmare. He only really remembers the fact that Nightmare is the boss, and responds accordingly whenever danger appears. Dust remains in the castle because he acknowledges Nightmare’s authority. Beyond that, he simply doesn’t care much about anything.

Inside the castle, Dust generally acts apathetic and detached. The only person he consistently reacts sharply toward is Killer, mostly because their relationship permanently solidified during the period when they absolutely despised each other after Dust first arrived there. Nowadays, though, it’s less genuine hostility and more just... fighting out of habit.

Dust had been left completely alone in an empty Underground. In the end, he succeeded in stopping the “human,” but all that really meant was that the human eventually grew bored and left. Nobody’s life or death was restored. He didn’t regret his choice — he still believed endless death and suffering would have been worse — but in the end, all that remained was emptiness.

As everything slowly wore away into silence, Nightmare appeared and tried to collect him. At the time, Nightmare only had Killer with him, and surprisingly, having another living being around inside the castle wasn’t nearly as irritating as he expected. In fact, he found it oddly satisfying.

That’s basically how Nightmare developed a habit of collecting mortals with emotions he found interesting. At the time, Dust’s emptiness had deteriorated to the point where it was almost comparable to Killer’s second soul state. Having fulfilled his goal, he had lost his will to continue and was slowly dying alongside his empty world.

Nightmare searched for something similar to Killer and eventually found Dust. He naturally tried to take him by force, but unlike Killer, Dust resisted violently. It was almost as though finally having something to fight against again reignited his will to live. That explosiveness only fascinated Nightmare more, and no matter how violently Dust resisted, he was eventually dragged back to the castle by force.

And after that... Dust completely lost his mind inside the castle too. Whenever he was conscious, he rampaged like an animal.

Whenever Nightmare was around, things were at least manageable — but whenever he left, Killer was the one forced to deal with Dust instead.

Technically, Nightmare had already warned Killer not to provoke Dust after he woke up, but after spending so long alone together in the castle, Killer became curious about the newcomer. Maybe he was even a little afraid of being replaced.

That curiosity turned into hostility almost instantly after Dust attacked him. The two of them fought constantly whenever they had the chance, and even Nightmare’s attempts to stop them rarely accomplished much. Nightmare acted irritated enough to want both of them disposed of, but at the same time, he understood that Dust couldn’t continue resisting forever. Dust was mortal, and exhaustion would eventually catch up to him no matter what.

Ironically, the reason Dust finally stopped resisting was actually something incredibly small.

Dust had completely collapsed onto his bed from exhaustion while Phantom Papyrus kept nagging him relentlessly that day. His stress kept building higher and higher until he was practically on the verge of exploding.

And then Nightmare appeared and simply started watching him with an amused grin, as though he were observing something entertaining. Dust wanted to snap at him or attack him, but then he noticed something strange.

Phantom Papyrus was floating beside Nightmare with the exact same grin on his face.

Seeing those two malicious smiles side-by-side somehow looked so absurd that even in his exhausted state, Dust found it ridiculously funny. A laugh slipped out before he could stop it. And somehow, that only made the situation even funnier.

Both Nightmare and Phantom Papyrus reacted to Dust’s laughter at the exact same moment, twisting their expressions in disgust and recoiling from him like they were suddenly horrified. Phantom Papyrus was annoyed that Dust was somehow laughing even now, while Nightmare became irritated by the sudden burst of positive emotion coming from Dust.

And somehow, despite everything, the sight was genuinely hysterical.

Dust started laughing like a complete madman. Maybe it was because all the emotions that had been spiraling inside him finally snapped all at once. Whatever the reason, he kept laughing while Nightmare and Phantom Papyrus both left in visible disgust. That only made it funnier.

So Dust stayed there alone, laughing until it slowly turned into sobbing instead.

The loud laughter echoing through the destroyed room eventually dissolved into quiet crying, and for the first time in a very long while, Dust allowed himself to laugh and cry completely alone. It was as though emotions he had buried for years suddenly burst back to the surface all at once.

After that day, Dust stopped resisting. He began following Nightmare almost as though acknowledging his authority. He felt strangely relieved somehow. He finally accepted that his goal had truly been accomplished.

The human would never return again, and his family and friends would never suffer endless death anymore. Having achieved everything he set out to do, he had simply been dragged into a prison built from his own sins. Maybe spending the rest of his existence there as Nightmare’s toy was simply the punishment he deserved.

So Dust behaves like an obedient prisoner. Though honestly... this prison never ended up feeling quite as terrible as he expected.

Dust doesn’t really care about much anymore, but he does see this place as the final destination of his existence. So naturally, he would obey child Nightmare too. After all, this is still Nightmare’s domain.

Honestly, the current form is a little ridiculous, though. Dust has had a tendency to see Nightmare as slightly ridiculous ever since that day. Maybe it’s because he saw him floating there beside his brother’s face like that.

All of them have some kind of relationship with Nightmare. Well... that’s only natural, really. After all, they’re all mortals Nightmare personally picked up himself. Regardless of how deep those relationships are, they all view this place as where they belong now. So none of them would truly doubt that the boss will eventually return, and the situation would probably resolve itself naturally.

If Nightmare never came back, though, things would become genuinely catastrophic... but well. I think I’ll avoid thinking about that for now, haha. This already became absurdly long and jumped all over the place enough as it is.

Thank you so much for reading! This turned out way longer than I expected... I guess I just had way too many thoughts built up about them 😳💦