HI EVERYONE. It's Solange, I have a new OC. Meet Agent X.
She used to work for Parallel Universe Patrol (like MiB only they deal with parallel universes and they're extremely corrupt). They did an experiment on her, injected her with nanobots. Nanobots are in her bloodstream, use her blood as fuel to give her body super strength/speed/healing (she needs to inject or consume blood to keep them running). They also make her immortal (only killable by complete disintegration) and make her hallucinate according to what her handlers want her to see. Her bots were hacked by another agency, who made her turn on PUP. After her recapture, PUP decided the experiment wouldn't be a total failure if they traded her to a creature in another universe. So they did.
The creature was an ascended being that fancied itself to be a demon, obsessed with Earth (of that universe) mythology. It made AX think she was a vampire, and changed her and itself over time to better match these labels. For 1,000 years she did the creature's dirty work, going to universes and other places it couldn't go, for assassinations and other missions. On a mission at a certain bar, a massive battle jarred her programming and let her see reality and think clearly for one second. An epic quest that won't even be touched on in this summary later, and she'd killed her old boss and gained a very powerful sword, then went back and destroyed PUP.
Right before the game, she's several years into her career as a mercenary/bounty hunter/space pirate/assassin, trying to figure out what the hell to do with her immortality and freedom.
Basically, she's a badass immortal that runs off faulty nanobots that occasionally make her hallucinate, but keep her strong, fast, and able to heal in supertime. She can also hop through universes (not anymore of course), make other people hallucinate by touching them, and teleport to anywhere she's been before. She feeds off blood (and food and stuff, and reeeally likes booze).
Because she's had 1,000 years of combat experience and missions to many many universes, she might even be familiar with YOUR pup's universe. This doesn't mean that she interacted with main characters from that canon or was part of any key plot points or anything- it simply means that she may have passed through and knows how that universe operates. If you want your pup to have known her, either as friends or enemies, from anywhere along her timeline (from when she was an evil creature's tool, or now that she's a neutral but usually immoral space criminal), hit me up so we can work out a backstory.
Journal is ParallelAgent, PB is a mix of two models: Crystal Zingsheim and Sabath. Replacing an NPC that works for Crowley's establishment. Wiki with much more detail is here!