Amulet: The Stonekeeper

Blurb

Amulet: The Stonekeeper is a 2008 children's graphic novel written and illustrated by Kazu Kibuishi. The book concerns the adventures of Emily Hayes, who must try to rescue her kidnapped mother with the assistance of her younger brother Navin, a mysterious amulet, and helper robots such as Miskit. Appropriate for grades 6–8 or ages 10–12, it is the first book in the Amulet graphic novel series.
Two years after a car accident that killed her husband, Karen has difficulties as a single mother. Emily, Navin, and the mother move to an old house inherited from Karen's grandfather Silas. The mother says that Silas was a "puzzle maker" who disappeared after locking himself in the house. While exploring Silas's library, Emily finds a stone amulet that had been hidden in a table, and Navin helps her wear it around her neck.
That night, the amulet tells Emily that her family is in danger. A noise from the basement awakens the family, and as they enter to investigate, Karen is kidnapped by a monster with tentacles.