Order of the Blessed Inquiry
The Order of the Blessed Inquiry are a non-militant order within the Adepta Sororitas who were tasked with research and study.
At some point in the past, they discovered the imprisoned form of the Keeper of Secrets Asteroth. But rather than destroy the Daemon, they sought to study it in order to learn more about potential weaknesses within Chaos. Thus, they kept the Daemon amongst themselves for three hundred years in secret and during that time, many of the Sisters were lost to the creatures lies. Eventually, it partly freed itself and destroy the convent whereupon it took their seven hundred souls for torture. Taking their ruined forms, the Daemon twisted their minds and forged the Screaming Cage as a work of art for itself. Whilst damned, the Order managed to resurrect the young Ephrael Stern and hide her presence from Chaos. In addition, they gave her great power and turned her into the Daemonifuge as a weapon against Chaos. Following this event, the existence of the Order of the Blessed Inquiry was lost to the Imperium.
Decades later, Stern returned and discovered the Screaming Cage on the planet Parnis where her past was revealed to her by the minds within the Chaos artifact. As their final gift to her, the Order transferred all their knowledge of Chaos into Ephrael's mind for her to use against Chaos. Some of this knowledge was later used to empower Inquisitor Silas Hand which he used to fight back the Daemon Asteroth. The soul of the dead Inquisitor later told Ephrael Stern to write what she knew in her own Codex and take it to the Eldar's Black Library.