This is an extremely good question that I've actually booted to the worldbuilding server to talk about.
If you didn't AU, I'd say yes definitely it matters for interactions with the in-setting angels and demons (they may respond to him differently than others), and he could also have some weird effects on the entire setting at your discretion. Similar to Illarion's corruption-shedding, but with whatever thematic elements you'd feel are appropriate for him.
For AUing, my initial thought (subject to change) is that you could go the "angel stuck in a person's body" route with him to parallel his canon situation. This would give him a different vibe with whatever magic he gets, and might get incredibly screwy if you wanted to also make him a shrike because the power of a Monarch opposes the Pillars of the World (the source of all the eldritch gunk shrikes have). So there's a really weird interaction here we would need to hash out and I'd be hype to do so. :D
ETA: For the AU option, "angel possessing a person" is a go.
no subject
If you didn't AU, I'd say yes definitely it matters for interactions with the in-setting angels and demons (they may respond to him differently than others), and he could also have some weird effects on the entire setting at your discretion. Similar to Illarion's corruption-shedding, but with whatever thematic elements you'd feel are appropriate for him.
For AUing, my initial thought (subject to change) is that you could go the "angel stuck in a person's body" route with him to parallel his canon situation. This would give him a different vibe with whatever magic he gets, and might get incredibly screwy if you wanted to also make him a shrike because the power of a Monarch opposes the Pillars of the World (the source of all the eldritch gunk shrikes have). So there's a really weird interaction here we would need to hash out and I'd be hype to do so. :D
ETA: For the AU option, "angel possessing a person" is a go.