Female authors are a mistake. Or at least this one is since she can't write a consistent character to save her life. While this wouldn't be a problem if the novel was just bolter porn, it's not that. It's fairly introspective and the bulk of the runtime is spent inside the internal monologue of our two main characters/narrators. They both struggle with survivors guilt, Evangeline the batter sister after surviving a face off against a lord of change on Ophelia VII (presumably the tyrant of blue flame). The other one is a schizophrenic inquisitor (literally, she can't differentiate between reality and prophetic dreams) on a quest to save her almost dead interrogator/lesbian lover. There are other characters but they get very little screen time and wouldn't you know they all also have some manner of survivors guilt.
Evangeline can be both extremely zealous, as a SoB should but also weirdly understanding at times. At one point a young sister under her command blindly charges into some kind of demon which results in another sister getting heavily wounded. Said sister just gets a stern talking to and they literally hug it out. But for the entire novel she thinks she's heading toward certain death and is completely fine with that. When that death fails to happen during the final battle, she decides to become a repentia becouse she doubted Big-E. . She also sometimes acts a bit marry sue-ish. Not only does she survive a lord of change without immediatly turning into fruit-by-the-foot, she gets marked with the titular mark of faith and is prophecized by the ecclisiarchy on terra to go and get the McGuffin, which leads to people literally worshipping her. To give the author credit she leaves it up to interpretation if everything involving her mark and prophesy was a tzeentch scheme or not.
The problems sart with Ravara, the afformentioned shizophrenic inquisitor. She's also bipolar but the pollar oposite of Evangeline. While Eva is a gentle souls who blames herself for everything that happens Ravara is the kind of person who wont take blame for anything ever. She's a very sterotypical inquisitor. She very quickly resorts to threatening anyone who dosn't agree with her, has in her past sanctioned exterminatus and all other fun stuff. She's also a seer, having prophetic dreams. So while lesser members of the Inquistion might result to lowly techniques such as interrogation and invesitgation to acomplish their goals she just dreams up the solution. She searching for a diffrent McGuffin that she belives will help her both close the great rift and heal her dying interrogator. As the plot progresses her shizophrenia gets worse and she starts seeing a ghost of her father. This time the author leaves no room for interpretation. Her visions and the ghosts are all part of a thousand sons sourcerer's scheme to unrubric his brother.. The issues with her are twofold. First of all the author clearly wants us to be symphetetic with her plight. Which is very difficult becouse her problems are entirely her own fault and as previously mentioned she's a very brutal cunt who probably killed billions becouse she dreamed someone will do a heresy. While very grimdark and a good idea the execution falls flat. You don't get to go 'I'm just a smol bean' as an inquistor. Second of all how did her powers not set off any alarm bells in the inquisition long before she earned her rossette. Seer powers are generally associated with the eldar and Tzeench. Not even the strongest human psykers could do that.