Recently, Games Workshop revisited the Sisters of Battle for Warhammer 40K by releasing a new official codex in the August and September issues of White Dwarf magazine. The reason for doing so is simply because the old codex was out dated, and included ally rules that are no longer in effect since before the release of the Grey Knight codex earlier this year. In fact, Games Workshop so badly wanted to kill those ally (and opposing corrupt army) rules that they posted updated PDF versions of both codexes with the ally rules redacted. With the new official White Dwarf codex, they also took the opportunity to separate the Sisters of Battle from the Inquisition, as they are the militant arm of the Ecclesiarchy.
"Quit your bitching, get off the computer and play the game."
