Shantak-kun is a female shantak, a Cthulhu Mythos creature manifesting as a bird with a horse's head and bat-like wings. She serves as the primary pet and companion to Nyaruko of the Nyarlathotep race. This creature possesses dramatic size-shifting abilities, ranging from rabbit-sized to the scale of a multi-story building. Her transformations extend to assuming functional vehicle forms, including a spaceship capable of interstellar travel; Nyaruko originally journeyed to Earth aboard Shantak-kun in this configuration.

Shantak-kun’s eggs represent a rare and valuable cosmic delicacy, consistently refused by the human Mahiro when offered. Demonstrating steadfast loyalty, she routinely aids Nyaruko through transportation assistance and mission support. Throughout all depicted media, her role remains focused on utility as a mount and egg provider, without expanded character development or background narrative. Her functions persist as a supportive entity defined by shape-shifting versatility.