When he consumes human blood does it kill them, turn them, etc? What are the rules on that in your head? Does he often go into bat form? If he does - does he like flying?
Anna started as a name scribbled on a paper. I'd decided to make my own group and make my own adventure, since every campaign I tried to play Ir'Vothgen in fell apart (even the same group, same people I've played other campaigns with, but if she's there it always falls apart. The games without her have been going on for years). So I wrote down Anna, Arlo, Elric, Karkash, and then went and decided Arlo was a full ranger initially, Anna a paladin, Elric a barbarian, and Karkash a rogue. I had already decided Anna and Arlo were siblings, but had made them twins. They sat in a notebook for about three or four years while I tried to outline a plot and figure things out. When my partner offered to do the roleply with me, I was ecstatic. I then nixed the idea of Arlo being a ranger and instead decided I wanted Arlo and Karkash to both be rogues, and Anna got pushed around as a result.
So I thought I'd make her as a side character. But then as I built Arlo I started adding more bits to her. She's 5 years younger, they're only half siblings, I decided she loves flowers because I wanted Irrie to be allergic to flowers. I thought if the group ever had to go to Arlo's mom's Irrie sneezing and coughing and having to sit outside would be funny. Then she just kept experiencing scope creep until she was her own fully-fledged character once again. And at that point ,I needed a fifth character. I decided to smash Anna back into the quint. Now there's technically two tanks and two healers in the party, what with Elric being a barbarian and Irrie being a cleric. But neither Irrie nor Anna specialize in healing, so they're only half-healers so it works out! And Anna is more the tank for projectiles (Shield of Missile Attraction) while Elric would be right in front punching the thing. So it all worked out!
When I had decided to replace Anna I was going to go with a tabaxi bard. But it ended up working out for the best that Anna's in the group. Because she's the only one who isn't neutral at best, so while the rest of the party has no qualms about theft she tries to keep them under control. Another bit that changed: I wanted to have their mom's place be more of a meeting place for the group, and Anna lurking and listening in for any crimes she could chastise them about sounded fun. But actually the group didn't really have a meeting place. Arlo's always at the Bag of Folding gambling, Irrie's at the library or temple of the twins, Anna's on duty or volunteering, Elric is at work as a bouncer, and Karkash is who-knows-where at any moment. They never really settled on a central meeting point due to not everyone knowing each other at the start of the campaign.
Originally, on paper, everyone knew each other. However, in the process of making them individuals who were forced together by fate, some things changed. Anna knows Arlo, Karkash, Irrie. Irrie knows everyone except Arlo (she's seen him with Anna and Karkash but hasn't spoken to him, does that count?). Arlo knows Karkash and Anna. Karkash knows everyone. Elric knows Karkash, Anna, and Irrie. So they didn't all know everyone, and as the game progressed those connections between people grew. Anna introduced Karkash to Irrie, who introduced her to Elric, etc.
Anna was supposed to be stand-offish originally, an apathetic person whose only joy was fighting. But Elric took on the 'love of fighting' bit, as I made him a gladiator in his free time. Anna grew into a more balanced individual. She's much more serious than the three goofballs -and I imagine her and Elric just watching the shenanigans go down with a sigh- but she's now a lot more loose. She'll drink, she'll dance, she'll have fun. She's not always quite as serious anymore, unlike how I originally envisioned her. Now - after the fall of Central City she gets much more serious. But honestly, everyone is going through changes. Arlo's drinking to excess, Irrie's going more feral, Karkash can't sleep, Elric is rambling, everyone's bound to be messed up after a cult traps everyone you know and love inside a dome. She'll be doing better soon. Just gotta sprinkle some angst on the group.
Some things she retained: She's a paladin. She's Arlo's sister. She's more serious than the others. She has a tendency to overwork herself. She's a bit of a neat freak. Doesn't like animals. She's still super big on the temple of the twins, still a paladin of Order.