The Atka are a group of spirits who dwell and appear most often in the North. Every person with Mer blood appears to have an Atka; it is unknown whether or not all humans do as well. The Atka are widely considered as malicious, but they live to protect the one they are assigned to. Only the Atka can choose when it is time for a person to die.
The Nanuq (polar bears) state that they cannot cross the Atka.
The Atka are described as looking like Mer with hair of silver, cold eyes, and skin as pale as the moon. Sapphire's Atka appeared to her sitting on an iceberg surrounded by fog, which covered her body, and wore a crown of ice.
The Atka appear to be able to take on the face of the person they are Atka to; Sapphire's Atka, after talking with her, gave herself Sapphire's face, with the main difference being in the colouring.
Sapphire's Atka - Sapphire's Atka protected her from the Nanuq and approached her while Sapphire was asleep. Faro woke Sapphire before the Atka could touch her.
Elvira's Atka - Elvira stated that she has meet and has been touched by her Atka, thus fuelling the reason she wishes to live in the North.
Faro's Atka - Faro states that if he was approached by his Atka, he would ignore him.
The Atka tend to have a chant they tell their charges.