Warpstone Flux Rating: ⭐️⭐️⭐️⭐️4/5 stars. The rules are good, but require some thought and planning. Consider warlord traits carefully.
Anathema.
All Sisters in this army are psychic blanks. This is given the name Anathema in the new rules. Non-psykers find them chilling, while daemons and psykers are actively repelled and suppressed by them. The first component of this is that no psychic power can target them. Nor can an area of effect psychic power get them (but can get other units). Even if there's one person in the squad with this rule, everyone benefits. They also cannot be hurt by force weapons - although they treat them as regular power weapons all the same. However, a unit that they're with that lacks this rule is at Ld-2 (and units in a small radius at Ld-1 - unless they're corrupted in which case they're also at Ld-2). Even stubborn units suffer penalties. The kicker is that although it doesn't stack with itself (just take the worst penalty in other words), it does stack with fear. The loyalist Night Lords just found their best friends in other words.
Chambers Militant (Sisterhoods).
There are 3 chambers - Vigilance, Oblivion, and Judgement. Players get an allocation of treble the number of units per HQ for each chamber (except Vigilance which is always available). In other words, if you have 2 Oblivion HQ selections, you get 6 other choices of units with the same Chamber.
Vigilance - These units gain Scout or Infiltrate (take infiltrate and run them with loyalist Alpha Legion and Raven Guard for extra friends).
Oblivion - These gain fearless when locked with daemons and corrupted - almost perfect for daemon hunting armies - or loyalist Word Bearers perhaps?
Judgement - Gain fearless when locked in combat with Psykers. Mortarion and Angron would approve.
Warlord Traits.
Maiden of Blood. An odd exchange. Take d6 wounds on your own unit at the end of combat and if anyone survives, they get an additional attack before the combat is resolved. Comes with an additional assault reaction. An interesting trait, and one that forces you to play hard and get into combat as soon as possible - take with Vigilance for the infiltration rule perhaps?
Maiden of Resolve. Once per game. Don't move. Don't run. Gain Feel No Pain. Gain Eternal Warrior! Pass any pinning and morale test. Very nice and the shooting reaction is good here. This is amazing really and could be a default choice.
Maiden of Sorrow. Gain Move+1 and A+1 for every unsaved wound up to +4 per turn until the end of your turn. Grant the enemy zero victory points for death in combat. The bonus movement reaction is strong. This trait begs to be used in a large unit that gets locked in melee. Take Alpha Legion loyalists for extra giggles? (The Mobius rite of war doesn't apply though - NB). Certainly a default choice here for large sisterhood attack units!
Overall.
Some really nice rules here, and several strong ones. If you know you're going to face off against psykers, daemons, and corrupted, you will ruin their day. If not, the Chamber of Vigilance is strong enough on its own with infiltrate.