It was the primary ingredient for the Ritual of Restoration.
By the late 20th century, since the transliteration annals for the ritual was lost, rendering the remaining text indecipherable until the efforts of Jenny Calendar in 1998, the sole application for an Orb of Thesulah was as a new-age paper weight. Rupert Giles himself owned one for this purpose.
The orb was known to glow brightly when held in a person's hand. Angelus lamented about the fragility about these orbs, blaming it on "shoddy Gypsy craftsmanship". Each time the ritual was successfully completed, the orb being used would dissappear as the soul entered the vampire's body, meaning orbs were not reusable.