What It Does
A taint, set in a cup, a well, a wound — the poison does not chase, it sets the terms, and the terms are already losing. It is the cantrip of the school: the rot is patient, and the patient is the one who wins by arithmetic, and the arithmetic is the one the camp has to drink.
The Cost
Circle 1 · Poison · Exchange: gesture — casting time one beat. On the ladder in The Veil, the gesture rung is the price.
The Failure
The taint is set in the wrong place — the broth is the one who is tainted, and the one who is not meant to drink is the one who is offered it.
In Stories
The camp's first poison spell; the one the serpent-folk cast when the cup is the argument and the terms are the ones who have to lose.
The door's scale anchor is Scorpion — the dragon casts it without thinking, which is how a reader learns the shape of the thing.