What It Does
The dark, set over a line — the names in the dark are taken out, one by one, and the line is the one who is not named, and the not-named is the whole argument. It is the master's dark spell: the line holds by the names, and the names are the ones the dark has taken.
The Cost
Circle 4 · Dark · Exchange: reagent (ash of a name, named) — casting time two rounds. On the ladder in The Veil, the reagent rung is the price.
The Failure
The ash of the name is named wrong — the reagent is the forge's, not the one the spell wants — and the dark is set, and the dark is the one who takes the name, and the one who is not named is the one who was already the line.
In Stories
The master's dark spell; the one the camp casts when the name is the argument and the dark is the one who has to take it.
The door's scale anchor is Shadowveil — the dragon casts it without thinking, which is how a reader learns the shape of the thing.