Oubliette
A dead slithering pit, tanned into a hole you can fold up and carry
A slithering pit is not alive and not thinking, but it moves: a hole that goes where it likes, slides itself under something, and closes. Kill one and the hole stays. That is what the party discovered under Haudh-Gwenn. The tunnel they were in ended at a rusted iron grate with no mechanism in it, a sealed one-way exit, and the stone door behind them had shut on its own timer, so they dragged the corpse to the grate, shoved it halfway through, and climbed down a rope to the riverside and out.
It was rotting by then, with a day or two of use left in it, so they took it to Greg the Tanner. What came back is a piece of hide that weighs nothing, folds down into something you would step over in the street, and opens into a pocket a few inches deep, uneven, shallower in places, never more than about six. Greg kept the better piece of the hide for himself. Tanners do.
For a long while it carried nothing more interesting than stolen paper and quiet loot. Then, outside the burning Color Stay, Koa went for Beltran’s wrist rather than his neck, because getting hold of the Wraithblade mattered more than killing the man who held it, and the sword came down in the street. Mikhail took the cloak off his own neck and went down on the blade with it, scooping up seven hundred years of bound souls without letting one finger touch the steel.
It held the sword and, at the same time, everything worth taking off Beltran’s body, which is the most it has ever been asked to hold and about as much as it can: a framed Eldamar-forest landscape out of the Silver Web’s command room had to be left behind in the den’s sealed room, because there was no room left in the pocket for a painting. The morning after Beltran died the blade came out again and went into the lead-lined box, which took one more turn of holding against it, and Mikhail has worn the hide as a cloak ever since.
What it carries now came out of the Twisted Grove. Unlit wood cut from the death-tree drains the life out of a bare hand closed around it, so the wood went into the lead box and the box was folded into the pocket, and nothing in there is drained at all. A cloak has no life in it to take.