The one who named it

The princess who was pretending

She arrives at the glass castle sent by her father, the King of Eyllwe, ostensibly to learn northern customs. She lets the court believe she has no common tongue and needs tutoring in it. Celaena — who speaks Eyllwe fluently — is assigned to teach her. The lessons are a cover for both of them, and become the only real friendship either has in Rifthold. Later, found alone in the royal library at night reading a high-level text in flawless common tongue, she stops bothering to pretend.

The marks

On Samhuinn she and Celaena see Cain drawing symbols in the dirt, and Nehemia names them: Wyrdmarks. An ancient written magic that Adarlan has made a capital crime, and she can read it. What she does with that is quiet and constant. She chalks protective wards on the floor underneath Celaena's bed without telling her. When the ridderak — the thing Cain summons through a Wyrdgate — savages her, Nehemia chants until glowing marks close the wounds. During the championship duel, while Cain is pulling creatures out of other realms, she is working the marks that let Elena through.

The argument

In Crown of Midnight she teaches openly — Celaena learns to read the marks and then to use them — and they talk about the rebellion as equals. Then she asks for the one thing Celaena will not give: swear to help free Eyllwe. Celaena refuses, afraid of what more rebellion costs, and Nehemia calls her the king's puppet and a coward. It is the last serious conversation they have. About a week before her death she walks out of Archer Finn's rebel movement, because she will not do what he is prepared to do.

The murder

While Celaena is away pulling Chaol out of a trap Archer set, the assassin Grave breaks into Nehemia's chambers and kills her and her guards. It was designed. Archer Finn arranged it specifically to break Celaena open and point her at the king. It works — she finds the body, and it takes Dorian's magic erupting for the first time to stop her killing Chaol over it.

What she leaves

Celaena hunts Grave down and kills him, then learns the shape of the thing: that Nehemia had understood the risk and stayed anyway. At the tomb she sings an ancient Eyllwe song and swears a blood oath over the body — to free Eyllwe, and to answer for her. Grieving and untrained, she later draws an archway of Wyrdmarks in her own blood to call Nehemia back, and exposes what she is doing it. The oath holds. As temporary regent in Queen of Shadows, Aelin frees every slave in Adarlan, and it traces directly back to a promise made over this body.