It's not that you LIKED being kidnapped by nightmares and put in cages with all your sisters. You didn't! You very much did not! It's just that you paid attention. Not only to his teeth, either; everyone was talking about his horrible teeth and how nasty they were, and how nasty he was.
It's just that you noticed. For a big bad bogeyman, Pitch Black was really scared. You could see him grinding his teeth all the time, and he always jumped when a nightmare showed up that he wasn't expecting. It was acid that made his teeth so brittle and yellow, because he was always waiting to be scared and couldn't ever relax. Also he was a nasty, bitter person who had locked you and all your sisters in cages, and he had taken The Teeth. You didn't forget this at all!
It's just that you listened to the moonlight. Your sisters couldn't hear him, and you never had before, but when it was very quiet and the bogeyman was gone, you heard him. Even when you couldn't fly anymore and you thought that your big sister might not come, you heard him.
It's just that everything had gone wrong. The moonlight told you so. Jack-Frost-With-Teeth-White-As-Freshly-Fallen-Snow had been supposed to fix what Santa-Claus-It's-A-Wonder-His-Teeth-Aren't-Full-Of-Cavities-From-All-Those-Sweets hadn't made, but then Jack-Frost-Etc hadn't fixed it, he'd made it worse. The moonlight said that it wasn't supposed to be this way, said that everyone had gotten it wrong and thought he'd said things that he hadn't said at all. Everyone knew that the moonlight always liked to have other people talk to each other for him. (You didn't tell him that you thought that was silly.) The moonlight said you would have to be very brave. So when you and your sisters could fly again (you knew your big sister would save everything!) and everyone was grabbing the tooth boxes and taking them home...
You stayed. You couldn't imagine being lonely enough to make friends with nightmares, but it got easier the longer you waited in the dark caverns under the bed. Even the nightmares had all gone away; it was just you and the moonlight, and he had stopped talking.
It was very dark, and very quiet, and your wings sounded very loud. At first you were careful to stay hidden and safe, but after nobody else was ever there, you stopped bothering. When the breeze blew, it rattled the chains and cages, and you tried to push shut all the cage doors you could. You didn't know why there were so many or what they were for, but you hated all of them, each and every one!
Then you heard the nightmares coming back, all at once. It was loud and you were scared and you almost trapped yourself in a cage by accident trying to hide. You didn't, though, you hid in a tiny crack between the musty old stones. Anything that tried to pull you out was going to get stabbed really hard!!
But the nightmares weren't paying any attention to you. They were - ooh, that was bad. That was awful. Even when he'd locked you and your sisters up, the bogeyman hadn't let the nightmares play with any of you. It was horrible to watch them play with him instead. You put your hands over your ears, but it didn't help.
There were so many nightmares, and they were all so big, and there was only one of you, and you were normal-sized. The nightmares had pulled the bed underground with them, you could see the old rotten wood lying in a heap where it had fallen. You didn't think anyone could get underneath the bed even if they tried. But nobody was going to try. Nobody would want to save the bogeyman, you knew they wouldn't.
This was probably what the moonlight had meant when he told you to be brave. Surely he wouldn't ask you for something you couldn't do? He definitely wouldn't. That meant that you could do this.
So you flew out of the crack in the stones as fast as you could, and you told yourself you weren't going to stop for anything. It was dark and the nightmares were big, but their eyes glowed yellow, and you just -- you stopped thinking about anything that wasn't you flying straight through that golden sand. Sometimes the sand darkened so that you could hardly see it (they were trying to eat you again -), but you pushed your way nose-first through everything that wasn't solid rock or iron bars and you weren't going to stop no matter what.
This time, it was the nightmares that screamed, dissolving away into the walls. And then - there wasn't any more sand, and the only yellow things were the bogeyman's eyes. You almost thought he was another nightmare at first, but then saw that he wasn't, and you stopped just a few inches from his nose.
The bogeyman was crying, and you didn't know what to do. You and your sisters cried, but not like this, not big scary gulping noises like you couldn't breathe or move or think or do anything but cry. You nestled between his neck and the collar of his robe (you were very, very tired) and patted his neck and told him that they were gone and that he was going to be okay, because you couldn't think of anything else to do. It was scarier than the nightmares had been, or maybe just scary in a different way.
You decided it was actually much scarier than nightmares when the bogeyman started laughing and crying at the same time. It wasn't nice laughing, and it probably wasn't very good for him. "A little... a little tooth fairy!" the bogeyman wheezed. "Four Guardians couldn't - and, hundreds, hundreds... and I couldn't - I couldn't..." He started crying again, hugging his knees. You very graciously decided not to take offense. There couldn't have been that many nightmares anyway, they'd've eaten you for sure. And he was the bogeyman, you already knew he wasn't nice.
He cried for a very long time, but it wasn't the same kind of horrible crying from before, and it got quieter and quieter until it was just tears. You... might have fallen asleep a very little bit by the time he talked to you. "Why?" the bogeyman wanted to know, wiping his face with a shadow-sleeve. "What could have possibly made you do such a - a stupid thing?" He swallowed hard, and you knew he was trying not to cry again.
You squeaked noncommittally. You didn't think he wanted to hear about the moonlight, or how he ground his teeth and jumped when the nightmares startled him.
"I don't understand," the bogeyman said plaintively. "I locked you in a cage! I stole your teeth! Why would you..."
You reached up and patted his cheek. The bogeyman picked you up and held you in cupped-together hands, looking at you as if he could find something that made you different from your sisters. (There wasn't anything, of course!) You smoothed down your crest and looked at him back. He wasn't nearly as scary when he looked all confused and reddish-gray from crying. His teeth were really bad, though.
"I... suppose you must be defective somehow. Maybe you hit your head on the bars."
Excuse you! You let him know just what you thought about that idea, and poked at his hand for good measure. There was a barely-scabbed over wound near his thumb that looked exactly like one of your sisters had done it.
This was going to be... harder than you thought. You really really hoped your sister was okay. You pointed at the mark and made a question noise.
"Don't... don't look at me like that," the bogeyman snapped, and you hoped you weren't imagining a little bit of guilt. You probably were. "I was - I had to teach that wretched Jack Frost a lesson!" His voice cracked a little on the last word. You also hoped that Jack-Frost-With-Teeth-White-As-Freshly-Fallen-Snow was okay, so you pointed to the mark again.
"I will not be judged by a - a scraplet of tooth fairy," the bogeyman told you vehemently, and shook his hand a little. You held on to a finger and poked him again to make him stop. He tried to explain about how he tried to make Jack-Frost-Etc join him, and then he tried to trade one of your sisters for Jack-Frost-Etc's ice staff heart, and then he didn't give your sister back because Jack-Frost-Etc had said he'd wanted to be alone and then your sister stabbed his hand and he threw her.
You knew he wasn't telling you everything. You wondered if your sister was okay, but the bogeyman couldn't tell you and you thought he was upset that you wanted to know. That was stupid and you told him so in no uncertain terms. Of course you wanted to know if your sister was okay! And no, you weren't sorry that she stabbed him in the hand! He shouldn't have done that even if Jack-Frost-With-Teeth-White-As-Freshly-Fallen-Snow had been mean to him! And if he didn't want everyone to be mean to him then he shouldn't have taken The Teeth!
"And now you're going to leave, of course," the bogeyman said, showing his horrible teeth at you. You gave him the worst glare that you could, but you thought you were figuring him out a little. He didn't want you to leave him alone at all, but he thought you would, so he was going to be mad ahead of time.
And of course you were going to leave sometime, to go see if your sister and Jack-Frost-With-Teeth-White-As-Freshly-Fallen-Snow were okay and to tell your big sister that the moonlight wanted you to do something for him (you weren't going to tell her exactly what), but it wasn't like you weren't coming back. And anyway you were much too tired right now to fly all the way to the Tooth Palace and back, even if you could get back underneath the bed, which you couldn't, because it was still down here.
You were pretty sure he wouldn't understand all of that, though, so you just flew back to his collar and made yourself comfy again. He didn't seem to know what to do about that at all, but you thought he could figure it out just fine on his own.
So you went to sleep. You weren't really worried about nightmares.