R's messenger

This individual was an unidentified, possibly Dark wizard or witch who cast the Full Body-Bind Curse on Jacob's sibling during the 1987–1988 school year at Hogwarts School of Witchcraft and Wizardry.

Biography
This person sent Jacob's sibling a fake invitation under the name of Silvanus Kettleburn to meet at the castle's Courtyard at a certain time at night. Upon Jacob's sibling's arrival, the person appeared, covering their face with a red cloak. They told Jacob's sibling about the forgery, claimed to be a "messenger" and promptly attacked the student with the Full Body-Bind Curse. After the petrification, the messenger said there's still time to avoid the same fate of Jacob and warned to stay away from the Forbidden Forest, the Cursed Vaults and Patricia Rakepick, and that "death is comming to Hogwarts" and that it may come to Jacob's sibling to if they disobey.