How to justify this character build thematically

Hey all,

First post. I had a character build concept that I really wanted to play but I am having a super hard time justifying it with fluff. I am much, much more fluent in Forgotten Realms lore than the Pathfinder setting lore. I am in a Kingmaker game and wanted to play a Slayer with the Ankou's Shadow archetype, and I wanted to use the Bladed Brush feat with a glaive to work as a sort of battlefield control character that doesn't have god awful dps (and this I can also take combat reflexes and all that).

All I know about Ankou is that they are evil fey, probably have something to do with shadows and stuff, and that they are maybe from the First World? The other issue is that Bladed Brush requires that you have Shelyn as your patron deity. She's the goddess of art, beauty, love, and music. How do I make these two concepts mesh and still feel believable?

Another note: the DM is a massive stickler for the rules, so there isn't any grey area or way to convince him to lift the requirements for Bladed Brush. I have to somehow be a devotee of Shelyn as well as have learned a combat style from an evil demon-fey thing.

All responses are appreciated, especially serious ones that are on-topic.

Thanks all.

JFM

So, thematically, I think an Ankou's Shadow is actually kind of perfect as a devotee of Shelyn.

Shelyn's brother became a god of darkness and misery, and she believed that he could be redeemed even after the terrible things that he did. She wields his glaive in his name, a horrific weapon that has become less evil in the time that she has wielded it.

So as an Ankou's Shadow, you have someone who was devoted to assassination and death. A perfect, harmonious killer who took great pride in his ability to hunt down and slay his targets without anyone even knowing that he was there. A monster, steeped in blood, knowing nothing but death. Maybe they started believing that they were killing for good reasons, and with each death they became more focused on the mission and less concerned with the harm.

But something changed. Maybe it was a target, or a target's lover. Maybe it was a mistake - the wrong person killed. Something got through to your character. Something opened their eyes to what they had become. And they looked over the rivers of blood that they had caused, and they despaired. They saw themselves as a monster. Who could love such a thing?

Shelyn could.

Shelyn's priests say that no one is beyond forgiveness. Not even a blood-soaked assassin. There is beauty and hope in everyone. And that has become the lifeline that your character clings to. You are still a focused fighter, but now you fight only to save others, in defense of love and beauty. You will not kill sentient beings, only monsters and demons. You are still honestly unsure that you can be saved, but your goddess tells you that you can, and you love her for it.

That's pretty much perfect. Thank you!

Glad to be of help! Let us know how the campaign goes.