The horn of a Horned Serpent is a wand core used by Ilvermorny founders James Steward and Isolt Sayre when they began crafting wands during the 17th century. This core is exceptionally powerful, sensitive to Parseltongue, and can warn their owners of danger by emitting a low musical tone.
Isolt had promised Chadwick Boot a wand when he turned eleven. The evening before his birthday, she received a dream of the Horned Serpent allowing her to take a fragment of its horn. Upon waking and visiting the creature, the dream proved true. She took a shard of the horn to her husband James, who was a skilled craftsman. He enclosed the horn core within a wand he carved from prickly ash wood, thus creating a wand of "exceptional power." The only other known wand with a Horned Serpent horn core belonged to Webster Boot, whose wand was also made by Isolt and James. They chose to reserve this core type for Chadwick and Webster alone, using other cores for the subsequent wands they created for Ilvermorny students.