The Order of the Terrible Glare was a malevolent religious organization, albeit with less spiritual beliefs than those of the B'omarr Order. In the Metharian Nebula, there were corsairs who were paid by the Order to capture pilgrims and deliver those captured to the Order.
The Order of the Terrible Glare was first mentioned in in the current Star Wars canon in Servants of the Empire: The Secret Academy, a 2015 junior novel written by Jason Fry. The Order of the Terrible Glare originated in the Star Wars Legends continuity, where they remained an obscure group with a select few appearances. In Legends, the Order was introduced in "Blind Fury!," a 1982 comic story appearing in Star Wars Monthly 159, written by Alan Moore and illustrated by John Stokes.
The character of Rur was adapted as part of the Ordu Aspectu in the second issue of the Marvel comic book series Star Wars: Doctor Aphra, written by Kieron Gillen and illustrated by Kev Walker. Since then, no connection between the Order of the Terrible Glare and Ordu Aspectu has been established.