Self-preservation is the name of the game.
Self-preservation is the raw gum on the left side of their mouth that they can't keep their tongue away from. It still tastes like iron, but their blood isn't staining the teeth they still have anymore. It aches in the way all broken things do when they want attention and will never be satisfied by what's given. They wiggle their tongue in the hollow again.
"There. Finished." What's between his fingers, bordered by nails kept immaculate and skin rough and peeling from the cold air that's leaking in, is a tooth.
It's also a suicide pill. It's a gift.
There are worse fates around them than death here. Self-preservation takes new forms. It's a choice they'd rather have then avoid looking at until it was too late.
They don't take his gifts before asking how they work. They're smarter than that. Or, at least, they know him better.
"And how do I keep that in my mouth without cracking it open on accident when I'm eating?" He draws the tooth, passably natural but veined with gleaming technology, back into his palm and closes his fist around it.
"Maybe you put it in, and it injects a toxin into your bloodstream instantly," he suggests. They trail their hand along the cold console. Poor defective thing. She struggles to carry them where they need to go, and she can't keep her own heart warm, let alone them.
"How does it work, Master?" they ask again. He likes hearing his name follow a question. He likes his threats being ignored less so.
"You clench your jaw," he says, annoyed, "and push it. It'll hurt, it'll pop, and then…"
"It'll hurt more?" they guess.
"You'll be dead soon. Does it matter what happens in between?" It does. He could have made it painless. "If you don't want it…" His palm opens wide, and the delicate tooth rolls down like he will let it fall to the floor. They move faster than they think. They catch the tooth against his hand.
They don't like touching him. It always feels like there's something more moving under his skin, something that grasps at their curled fingers and reaches into their cells until they drag their hand back. His expression hasn't changed, but they're grimacing and they hate it. Their face melts back to something safe and blank. "I want it." The tooth is warm where it sits in their fist, and they aren't thinking about that.
"Put it in, then." There's an awful smugness radiating from him. They almost want to try, but they don't want to die here. Not this frozen TARDIS, not with him, not on this moon so small it isn't named beyond numbers — none of that matters. They don't want to die here, inside of it all, where time echoes back and forth until even someone- something like him can barely stand it at the loudest places. They didn't come all this way to die in another cage.
They will die somewhere that death matters. That's all they want.
So, they don't struggle with the tooth and put their own life in danger like a fool. They let him take it back, and if he takes the chance to kill them, then at least he is something that can change and live and escape. If he kills them, he takes them with him, whether he wants to or not. And if he is ever free-
He tries to touch their jaw, and they recoil.
"I have to hold your mouth open to get it in," he lies. They bare their teeth, nothing special, nothing particularly sharp about them. He's hesitating all the same.
"Take your chances," they say.
If they are crossing this channel together, then they want to be able to sting him.
They open their mouth for him. They reveal their missing canine, waiting for its replacement.
They feel his fingers against their lips and teeth. They hurt where they press against their gum. He tilts their head with a little pressure to see the empty space better. They stay still. Their breath fans out across his hand.
It hurts. They inhale sharply. Metal, not bone, digs into their gum. It pierces through and burrows until it's secure. Their gum bleeds again.
His fingers rest against their lower set of teeth. He's surveying his handiwork.
They close their mouth around the tips of his fingers. He barely has time to react and yank them back. They still catch the skin at the edges, digging in until blood spills out and the rest of his fingers come out scraped pink and raw. They lick their lips. Their new tooth, battered by the sudden movement, doesn't break, doesn't kill them.
"You bit me!" he snaps. They brace themselves against the console, but all he does is hiss and retreat.
"I did!" His blood doesn't taste like theirs, not exactly. They resist the urge to touch their new tooth. That feels too much like tempting fate. "How does it look?" He glares at them, bloody fingers held to his chest. Really, it was only a nip. They barely tore the skin off. They could do worse.
He would know. He would…
They don't want his blood in their mouth, suddenly. There's too much of it. They spit, but the taste lingers.
It's futile. He made the tooth. Part of him, lodged in them, poisonous. Death preserved inside, like a bullet, or like a moment, the seconds wrapped around a shove from surprise to terrible impact to puddling blood below a still body. He made this.
Even asked for it.