TW, for mildly(imo) gorey and vaguely graphic imagery? idk, but it may be a bit much for some people, so just in case.
So! one of my most common personal headcanons is Blue with a tail. Long, thin, he can use it as a whip or an extra arm to carry stuff. If i combine that with my other common ice magic headcanon, i imagine him using his tail like a deadly nadder from httyd.
But, he's not the focus here.
So, as we all know, Dream and Nightmare's physical forms are based off of underswap sans. Assuming it's this Blue specifically, which i like to believe it is because why not, then they should also have tails. Yet I never seem to imagine that for them.
So! Angst potential! They both have their tails docked. Well, not really. Docked would imply it was done for a reason, and not in an excruciatingly painful way. But this is angst potential, so of course they suffered.
For Nightmare, i imagine it happened early on. Same base idea, the villagers being assholes, pushing him around. Only this time, they decide he isn't allowed to just brush things off, forget they happened, pretend everything is alright. They hold him down. This isn't new, it's happened before. But the knife is different. They grab his tail. You can put two and two together. He's left with barely a stump. It hurts. It's bleeding. They had cut his tail off piece by piece, always cutting into the bone itself, before finally lopping it completely off. It was awful. He couldn't hide this one from his brother, couldn't brush it off. It's one of his last straws.
For Dream though...this all depends on what personal variation of his story I'm going with. So, starting with my most common one. In this version, Dream finds out what the villagers are doing to his brother, and confronts them. But, in typical(to me, at least) Dream fashion, he offers himself up in exchange for Nightmare's safety. They follow it for about three days, then continue to hurt Nightmare without Dream knowing. In this version, Dream's tail would be cut before Nightmare's. The villagers had to see if it would work, if it would be painful. It is. They slice through one of the vertebrae, instead of the space between. It sucks. It hurts like hell. Dream doesn't let Nightmare know. Then he becomes stone and never finds out that it happened to Nightmare too. When he finally sees his brother's tail, or lack thereof, he's in tears. Because that's how he really figures out that he was the practice dummy so they could keep hurting his brother.
For my other version, it follows typical Dreamtale(i think). Dream is kept oblivious, Nightmare is hurt(tail gets cut off), apple incident. The whole shebang. Then he wakes up, five hundred years later. He has his tail, though he hides it now, a habit he developed from Blue, who does the same. Apparently, long-tailed skeletons aren't always appreciated. Why, he doesn't know or understand. But whatever. Now, maybe a villager or two survived the initial purging of Dreamtale. Maybe Core found them and saved them. Idk, i'm not well versed here. But maybe they're in the Omega timeline. Maybe time flows differently there. Maybe they're still alive. Maybe they see Dream, remember his brother, and decide to get revenge the only way they can.
Dream doesn't fight back. Not initially. He's too confused, this person, these people he had thought were his friends so long ago...they admitted to hurting his brother. And now they were hurting him too. He lets it happen. He believes he deserves it. Or maybe he's just too stunned. Point is, he doesn't fight. By the time his tail is getting cut, he's crying. Silent tears, from guilt, from pain. Anger flares up, for his brother, for ever trusting these cruel people. Then his tail is gone and he's left there, in pain, crying quietly. It's half an hour before Ink finds him. Blue was there less than a minute later. Dream could fee his anger, sympathetic pain. And sadness. Tails were hard to grow back, even for an immortal. For one who's vessel isn't even their true body, impossible.
In this one, when the brothers meet outside of battle, Dream is already hugging him. In tears, apologizing for everything, for never knowing, for the pain he couldn't save his brother from. He has a weak smile when he says they match, that he has at least some semblance of an idea of what happened to his brother. Nightmare is floored. The remaining Dreamtale villagers are dead before night's end.
anyway, angst potential from basing them off of Swap specifically :)
on a nicer note, docked tails can still wag. Dream doesn't mind it when his does, he just gets doted on, causing more wagging. Nightmare has nearly torn Killer apart for a teasing remark. He thinks himself above it. He is not. His tail(what's left of it) will wag when he sees his partners subordinates happy.
