A “single sibilant word” in the snake-language Parseltongue that when uttered made the wand of Salazar Slytherin go to sleep and become unusable (Pm).
- Gormlaith Gaunt, a Slytherin descendent and Parselmouth, spoke the word as she was about to attack Ilvermorny School and take revenge on her niece Isolt, who had stolen the wand years before. It quivered once and became inactive (Pm).
- The twins Chadwick and Webster had wands with twin cores of River Serpent horns. Instead of going to sleep when the word was uttered, their wands awakened to the sound of Parseltongue being spoken. Each wand emitted a musical note warning of impending danger (Pm)
The implication is that the Basilisk horn core of Slytherin's wand could "hear" the word and obey the command to sleep.