- "...the wand of Salazar Slytherin, one of the founders of Hogwarts, and that it contained a fragment of a magical snake’s horn: in this case, a Basilisk. The wand had been taught by its creator to ‘sleep’ when so instructed, and this secret had been handed down through the centuries to each member of Slytherin’s family who possessed it. "
Salazar Slytherin owned a wand of his own making, made of snakewood and with a Basilisk horn core. The wand had the distinction of being able to 'sleep' when so instructed, an ability taught to it by Slytherin himself. After his death, the wand was handed down the family: by the early 1600s it was in the possession of the Gaunt family.
The wand was stolen by Isolt Sayre from her aunt Gormlaith Gaunt in 1620, when the young girl fled to the New world aboard the Mayflower. Once in America, she used the wand around the time of the founding of Ilvermorny School of Witchcraft and Wizardry. The wand was deactivated by Gormlaith herself when she tracked down her niece and, following her death, the wand permanently wilted. It was eventually buried at Ilvermorny School of witchcraft and Wizardry where it grew into a unique snakewood tree which leaves contained powerful medicinal properties.
During the 10th Century, Salazar Slytherin, one of the founders of Hogwarts School of Witchcraft and Wizardry, decided to make his own unique wand of Snakewood with the core of a Basilisk horn, a dangerous giant snake that was bred by Salazar himself and who lived in a hidden secret room at Hogwarts. The creator gave this unique wand the ability to sleep and to wake up again when instructed by speaking Parseltongue to it, a rare gift that gives you the ability to speak with snakes that only descendants of Salazar Slytherin possess. After Salazar Slytherin's death, the secret had been handed over through the centuries to each member of Slytherin's family who possessed this wand. By early 1600s, this wand was in possession of the Gaunt family.
At some point before 1600, the wand was in possession of Gormlaith Gaunt. Gormlaith used the wand to burn down the cottage of the Sayre family that tragically killed Gormaith's sister and her husband, saving her niece Isolt Sayre out of the fire to raise her at her own, with the hope that she can bring Isolt back to the ‘right way'. Gormlaith had also used the wand to curse and jinxe any Muggle or animal that strayed too near to their cottage, where she lived with her niece. Isolt Sayre stole the wand from her aunt in 1620, and fled to the new world by aboarding the Mayflower. Once in America, she used the wand around the time of the founding of Ilvermorny School of Witchcraft and Wizardry. However, Isolt had never known that she held in her hands the wand of Salazar Slytherin. While tracking down her niece, Gormlaith sent a powerful curse containing Isolt and her husband’s names towards the house, which forced them into an enchanted slumber. Gormlaith uttered a single sibilant word in Parseltongue, the wand quivered and became inactive. When Isolt and her husband was awakened out of their enchantment because of the cries of their twin daughters, Isolt tried to stop her aunt together with her adoptive sons, but it was useless with a deactivated wand. In the end, Gormlaith dies by a poisonous arrow of William the Pukwudgie.
- "Within a year an unknown species of snakewood tree had grown out of the earth on the spot where the wand was buried. It resisted all attempts to prune or kill it, but after several years the leaves were found to contain powerful medicinal properties. This tree seemed testament to the fact that Slytherin's wand, like his scattered descendants, encompassed both noble and ignoble. The very best of him seemed to have migrated to America."
- —Slytherin’s Legacy[src]
Slytherin's wand remained inactive following Gormlaith's command in Parseltongue. Because Isolt could not speak the language, the magical wand could not be activated anymore. Although, Isolt decided to bury the wand outside, as she no longer wanted to touch the wand that was the last relic of her unhappy childhood. By the following year, a magical snakewood tree had grown out of the earth on the spot where the wand was buried. People tried to prune or to kill the tree over the years, though the tree resisted all attempts. After several years, the leaves of the Slytherin tree were found to contain powerful medicinal properties.
- Pottermore (First mentioned)