I carry a small clutch of teeth on a ring of bone. Cold teeth. Sharp and jagged, each one bitten in a different pattern, and each one belongs to a different mouth.
This tooth wakes the cave door. I push it into the door's throat, I turn, and the door lets me pass. It knows my tooth from all others. If I lose the tooth, the door does not know me. I could beat it, I could scream at it, and it would keep me out in the cold like a stranger, like an enemy, like meat that wandered too far from the fire.
This is the strange thing. In my old life, a den was mine because I was strong enough to hold it. Here, a den is yours because you hold the right tooth. The tooth is the strength now. A small child could carry my whole life on one finger and walk into my fire and I would have no home.
So all day I touch the ring in my hide. I feel for the teeth. When they clatter, I know my dens still open for me. When they are silent, my hand goes cold before my heart does.
We have made our safety small enough to drop in the grass.