Your character has been bitted by a Vampyr! And they’ve done a foolish thing - they stayed on a planet for too long. What do they look like as a horrible cancerous monstrosity?
I remember a bunch of people joking that if Mir ever got infected he'd just turn into a velociraptor, so a velociraptor.
I can only think of two characters' outcomes in this situation. Arial would probably end up turning into some kind of small-but-agile mutant. One that's anatomically specialized to be quick, and lives in areas that are outdoors but almost constantly in shade, like mid-density forests. For some reason, grasshoppers or crickets come to mind; more specifically, their huge and distinctively-shaped rear legs that let them make huge leaps at a time (hence why she'd be something not much larger than she was "originally," if even that - so she's light enough to make use of that feature). That being said, she is a metanoid, so I have no idea if the advanced stages of FEV would actually drive her insane and feral like a fully-organic person. Since she's an SI meant to be as convincing as possible, it probably still would. Then there's Eli. I'm not sure if FEV is capable of leaving the victim with such a "glamorous" end mutation, given the visual references the Vampyr page gives, but with him, I see something similar-looking to Halo's sangheili ("elites"). Something still upright and bipedal, exhibiting finesse and behavior reminiscent of when he was still human, but is distinctively not human and instead very alien beyond overall silhouette. A body that's lean and nimble, but up to twice as large as an average human, with almost everything about its form being highly function-over-looks. Ugly by our standards, but for practical reasons, rather than being horrific just for the sake of it. This all being said, Eli is such a huge body purist that I doubt he'd let it progress this far at all; he'd go around to every place and person he can find to get the virus out of his system in the early stages if he can. If that were to fail, he'd take advantage of also being a metanoid to just have a new body cloned and have his chip/implant that has "him" on it moved into that new body, then destroy his old one. Failing that - like if he were fully isolated or something - he'd go as far as to kill himself if he started to notice mutations in his body outside of going pale or growing fangs... though since that takes years upon years last I checked, I doubt it'd come to that, but it goes to show just how obsessive he is over "human purity," at least on a personal level.
wow what a coincidence haha my character was gonna have a puffy lamia vagina just a thought experiment though ...unless...?