Seer

"Tending these graves and guiding the Wielder... all penitence for old crimes. Certain things have to be kept in balance."

- Seer

The Seer is a Quest NPC in Hollow Knight. She gives the Dream Nail and grants rewards depending on how much Essence has been acquired.

Lore
The Seer is the last surviving member of the moth tribe. She tends the graves of the Resting Grounds and guides the Knight because she regrets that her ancestors forgot about their creator, the Radiance. When the Knight has collected 2400 Essence and returns to her, she explains more about the history of Hallownest, after which she dissipates into Essence.

Hollow Knight
The Seer brings the Knight back to her house after they are trapped in the dream realm by the Dreamers.

She gives the Knight the Dream Nail, which grants access into the dreams of NPCs and enemies along with other abilities. She then urges the Knight to go and collect as much Essence as possible in order to fully awaken the Dream Nail.

Trivia

 * It is implied that the moth ghost who guides the Knight out of the Dream Realm is the Seer, projected into the Dream Realm through unknown means.
 * She can also fly in this form, though she seems unable to when she is met physically.
 * Seer is one of the few NPCs who are able to detect when they are being Dream Nailed, the others being Bardoon, Midwife, White Lady, and the Snail Shaman.
 * The journal entry for Nightmare King is a poem by the Seer.