Asafia's bargain

There's a discussion over on the Clarion Foundation blog about teasers, which in this case means choosing excerpts for brief readings.
The following may be too long, but I think it stands reasonably well on its own. I may be too close to the story to judge.
A scene added in the last revisions of The Willow Knot to flesh out the Wicked Aunt:

Asafia stepped into the marshwater, and black mud rose about her bare feet, dabbled at the hem of her white shift. The fat moon bleached hair and skin to like pallor with her linen. In her arms she bore bundled cloth.

"I have woven," she said to the darkness. "I have woven strong within and without, for the love I bear you and for the gifts you give."

"Weaver woman," said the darkness. "What do you bring me?"

Asafia shook her burden out, in meshes that caught moonlight with shadow. "A net to snare birds. To snare frogs. And those who pass between shapes shall not pass through this."

The darkness reached out with hawk's talons to hook the net, with stumpy fingers to worry at the knots, with a blunt muzzle to snuffle at the cords. "The strands sting. What virtue have they?"

"Strands of courtesan's hair for the snare of lust, plied with threads of shrouds for the grave that none escape. Washed in the tears of an infant, the monthly blood of a virgin, and the spittle of a crone."

Could she have learned the craft of House Sallew, those knots that sealed the king's secrets, how much more power would her net have? But that was an old grievance, and Asafia put her niece's sullen obstinacy out of her thoughts. This prince of the marshes was cunning, and she must not be careless.

Its tongue rolled out, touched the net and shrank back snail-like. "What ask you for this?"

"A flask of nix-water." She added, "And safe departure from your lands."

The muzzle flattened to a child's pouting mouth, sharp teeth showing as the upper lip drew back. "The night'll come that you forget, and I'll have your blood and bones."

"Then who should make you a net to snare the silver birds?" Asafia threaded scorn into her voice. "You'd sooner have one dish than a hundred meals?"

It squatted at her feet, shapeless as a trick of weary eyes. "Such a dainty dish that one would be, white as swan's flesh." A stinking sigh fluttered her damp skirts. "Well then, clap hands on a bargain." It held out fingers like rotted twigs, and Asafia took them in her clean hand, felt them yield in her grip like a cluster of frog's eggs. It giggled. "Be one with me, you'll need no nix-water to change your shape."

Asafia said, "To be consumed comes to all mortal flesh without your aid. Give me my flask."