Sisters of Battle: The Imperial group of warrior women who were first founded in the Age of Apostasy. Originally a female sect located by High Lord Vandire, he twisted them against The Emperor.
The 'Decree Passive' forbade the Ecclesiarchy from maintaining 'men under arms' and so, in keeping with the letter of the decree, the warrior women became the army of the Ecclesiarchy. The convocation of Nephilim then bound the Sisterhood to the Ordo Hereticus.
Source: White Dwarf: Issue Unknown by Unknown
Submitter: IBBoard
Hive World Terra