Soooo, tell me if I get it wrong, but grim are like human who dies and reincarnates in a other things ?
If that right what would your main character will look like as a Grim?
No, it's not reincarnation. Grims are dead humans who are just attached to something/someone (their host) that anchors them to the living world, i.e. that keeps them "alive". No reincarnation, once their host also dies or gets destroyed they're gone forever
Now, here's grim!Eiko :]
TW: Nudity (but no detail. She's based on marble greek statues but she's as smooth as a mannequin, no genitalia or anything.)
Thinking about grim Eiko was really fun, but also tricky because the first step in making her a grim is deciding when and how she died. Is this an alternate universe where she died when she was younger, or does she die later down the line when she's already her "default" age? I decided to go with later, because I didn't feel like aging her down. "Base Eiko", to me, is 19, so that's what we're going with. Although some grims, in rare and special circumstances, do keep physically aging, I don't think that'd be the case for Eiko.
So how did she die? Her dying at 19 years old implies she dies during the course of the story, so it's basically just an Eidolon bad ending scenario. I don't want to say Eiko will have died during the final big climax because, although it would make sense, it'd also mean the plot would be resolved by the time she was dead and it wouldn't leave much for Hayato to do aside from. wallowing in pain and grief. Plus I don't want to spoil said climax. So we're going with a compromise: Eiko dies later in the story, but not right at the end.
The cult has a history of taking out people when they realize they know too much about them and/or seem like they're snooping around. Usually in such a scenario Hayato would be able to stop them in time by either promising to take care of it himself, or convincing them some other way that she isn't a threat. In this instance, he'd have failed. Eiko is killed = wrongful death = becomes a grim. I know the coolest option is to make the host a person, in this case probably Hayato, but, as cool as it is, it does sort of take away part of the fun that I can have with the design since the host needs to influence the grim's appearance, and I don't think grim Eiko being Eiko but scary with some of Hayato's features would be a very cool design, and certainly not the one I want to go with exploring this AU. So we're going with an object grim. Fyi, grims don'f consciously choose their hosts, just like how they don't consciously choose to become grims.
If you want an explanation in this AU for why Hayato didn't become her host, here's what I've thought up: maybe when she got ambushed, she thought Hayato had betrayed her and for whatever reason had wanted to have her dead. Yes it's jumping to conclusions but you gotta remember the massive gamble she's taking by trusting the guy who is also the prince of a cult. She didn't think or expect he'd betray her but she should've kept in mind it was always a possibility all along.
Grim Eiko's host is her sword. I haven't talked about this actually but Eiko has a lot of affection for her sword, it's a symbol of pride to her. And it was also her last line of defence before she died. I think this may be a lame answer but idk I don't think most other PCD agents are that fond of their weapons. Eiko is because it represents a lot of good things to her. She'd be a corporeal grim, and for her appearance I decided to make her look like a damaged statue. I don't think this'd correlate to how she died, mainly because I can't think of an interesting cause of death. Since it was something like a hit, I think it would've been too discreet to impact her appearance.
Why does she look like a statue... I think you could interpret it many ways. Statues are usually made in the image of someone to honour them, but Eiko, being damaged, would represent her losing her honour and dignity when she was killed. Or, she died thinking she'd been betrayed, so she's got nothing but stone in the place of a heart now. Or, she's a literal pale imitation of who she was before her death. Or, she died because she was so weak and fragile she couldn't protect herself, so now she's bulletproof, but she's also impossible to get through to. She has her sword, so she's like the knight protecting her own walls she's built around herself. She's confused and hurt, so she lashes out at everyone, forever stuck in a state where she thinks she needs to protect herself because she's always reliving her final moments in a loop and can't tell it's been over for months.
I do not think this AU would get better, it would be a nightmare for everyone. If Hayato's already doing bad in canon he'd be Suffering in this timeline. I don't think he'd be able to get through to Eiko, or convince her that he didn't betray her. Or, if he did, that'd be when her stone body would crumble and she'd be gone forever (technically her sword would have to be destroyed for this to happen yes but go with it).
Oh yes, I almost forgot. Her ability is a bit tricky. I have 3 options I like: petrification, a.k.a. turning people to stone by staring at them, a literal death stare, people die when they make eye contact with her, or, to play into how her sword functions in canon, she drains people of all their blood once they're stabbed with her sword. They'd also end up looking like her, since if you drain a person of blood, they become you know. really pale. I feel like this last one is a bit too dramatic and violent- idk, but I had a lot of fun thinking of this version of Eiko.