Name: Klythie Costas.

Alias: Sea Witch.

Personality: Klythie has a kind of contradictory personality - friendly but with an aura of aloofness, sometimes easygoing and sometimes nitpicky, by turns superior and humble and a complete fish out of water. It comes with the territory of lacking human role models early in life, then later choosing a pretty strange one to model herself after, all while trying to sort herself out internally at the same time.

Physical Description: To paraphrase Christian Bale, Klythie gives off friendliness with nothing behind the eyes. She often wears a slightly forced smile that shows very white teeth, and she seems a little uneasy in her own pale skin. She has very long black hair, exceptionally dark and vaguely sharklike eyes, and a tall, lean build. Her clothing choices are formal and old-fashioned, and she's never without a hat, cane, gloves, and some form of neckwear.

Her fake-seeming friendliness is actually due to ongoing difficulty matching feelings to their expressions in a natural way, rather than falsity of the emotion itself. When she's letting her hair down, her feelings come across more naturally. Of course in that case they're coming from a much more alien form, which can also give people trouble. What with the three inhuman eyes, the white and purple skin tones, and so on.

Powers:
*Shapeshifting: Can assume any human form, usually as a disguise, though she doesn't copy powers or even physical traits like exceptional strength. She actually blends in better when impersonating someone else, it's "acting natural" as herself that trips her up.

*Natural Gifts: Can breathe underwater and survive extremes of temperature and pressure, regenerate injuries quickly, and animate her hair into several tentacles to strike or grapple targets or just for extra utility. Her alien anatomy protects her from most poisons and illnesses, though not hazards like fire, acid, or electricity. That alien anatomy also doesn't make her exceptionally strong - she can outfight normal humans but not most of the threats that would call for a planet-level hero. Nor, for that matter, is she generally a match for the heroes that do that kind of thing, with the possible exception of getting into a fight underwater where she has natural advantages. She has keen senses of smell and sight, the latter of which is helped further when her third eye is open.

She carries a remnant of a magical, mind-warping infection, though she absolutely will not try to spread it. Because of that, her mind is so internally alien that mind reading and mind control aren't just ineffective, they risk infecting the actor in question. By the terms of a peace agreement between the governments of the world and the dangers of the deep sea, if that happens it's off to the sea floor for magical treatment and a severe tongue-lashing.

*Magic: Klythie is a magician, but not a very powerful one after being cut off from one of her original power sources (her grandmother) and living very distantly from the other (the arcane foci of the deep seas). She does best where theory counts for more than brute force - i.e. against other magicians, whether by analyzing the scenes of magical crimes when mundane police come up short, or counterspelling and dispelling active magical threats. Many hedge-wizard villains can be downed by a quick combo of a shield-negating spell and a cane bash to the face.

Klythie has managed to get a couple of minor spells under her control again, such as conjuring and shifting clothing for when she shifts form, and a minor healing spell for stabilizing injured civilians in an emergency. She can show off somewhat with her natural forte in water magic, but not do much practical unless it's putting out fires or purifying it enough for people to drink safely. She's much stronger in the deep ocean, especially with water magic, so if aliens ever try to invade the Marianas Trench, they're in trouble.

Skills:
*Detective: Klythie absolutely idolizes Hercule Poirot, to the point of trying to emulate his signature abilities. Of course she failed to reach such heights as that, but she does have a private investigator license and works as a private eye in her mundane identity. While she lacks the ability to solve a case from a critical throwaway detail, she has managed to train herself somewhat in methodical analysis and investigative techniques, and her enhanced senses help as well. She's especially good at solving cases that were obfuscated with magic.

*Martial Arts: Due to a lack of super-combat abilities beyond survivability in her powers, Klythie has to work out and practice fighting the same as any civilian. Since Poirot never actually fights anyone but does carry a cane, she turned to Sherlock Holmes for extra inspiration and trained in bartitsu. Poirot disdains guns and taking lives in general, so she does too.

*Fangirl: Some of the things Klythie has picked up are just silly, but might have utility in corner cases. She's learned fluent French just so she can pepper her speech with it, for example, and learned how to cook so that she can prepare things like hot chocolate and tisanes. Sadly she actually finds tisanes really gross, but she does love hot chocolate and can make an excellent pot of it on request.

*Occult Oceanographer: Klythie lacks the broad knowledge to call herself a fully qualified marine scientist or scholar of the esoteric, but she does know the intersection of the two pretty well. If you want to know about, say, the Bermuda Triangle or the Sargasso Sea, she can probably help. She also knows several languages of the nightmare creatures of the depths, who generally treat her with  at least professional courtesy, which she returns.

Notable connections/assets: Klythie's "grandmother" is a terrible power of the seas, and her siblings have leaned more into the monster side of things than she has. Klythie is the only one of the family that still embraces her human heritage; it hasn't left them estranged, but there's a definite distance, and they'll only assist her endeavors (and by extension humanity) in a serious emergency. The divide is only political though. They still get along otherwise, and the undersea "door" is always open for her to drop in. She usually visits about twice a year, which involves jumping out of an intercontinental flight.

While it's not exactly notable by comparison to that, Klythie has a one-person, one-office private detective business. She lives with her adoptive human parents. She doesn't actually need to work, due to her ability to collect gold and other treasure from deep-sea shipwrecks, but she derives a certain satisfaction from blending into human culture when she's not doing heroic stuff.

History: Klythie's story starts with her grandmother, who would eventually be known as the Deep Source, or sometimes Pth'thya-l'yi by the more literate hero-and-villain commentators. An ancient, dormant magical threat, the creature (generally later assumed to be female) was awakened three decades ago by a high-tech deep-sea expedition. The Source seized the vehicle and assimilated its contents, giving it a new source of intelligence and technological understanding, then sent out its new mutated drones to begin attack and infecting more "materials" for its expansion.

The heroes of the human world realized after a few ships lost at sea that there was a serious threat going on, and while it was hard to reach for attack or rescue operations, they were able to pin down the Deep Source and its drones in the deep water for safety. The Deep Source responded by creating a new generation of shapeshifting, completely biological "children," then deployed them to the surface to scout and find weaknesses to be exploited.

The major wrench in this plan was that the sleeper-agent children, Klythie included, went native almost immediately. Being incarnations of a magical mind-virus left them free-willed, like a child inheriting an immunity from a parent, but simple filial piety wasn't enough to keep their human sides from realizing what they'd been missing when they reached the surface world for the first time. They also had a strong imprinting drive that went kind of awry, as it was meant to help them blend in quickly but often caused the children to overly mimic others around them or even celebrities.

It was only a matter of time before one of the changeling children was exposed, and then for all of them to be once the threat was recognized. Curiously, as alien as the Deep Source was, it did have one recognizable trait: a maternal instinct. As such, a deal was struck with her. The children were turned over to her safely, and in return, her existing kidnapped "drones" were restored to humanity and disinfected before being returned to the surface. She also pledged to leave the surface alone in return for being left alone herself, to devote her magical energies toward researching interplanar transport. At this point she wished to move with her family to a different world that wasn't so bothersome.

All of this doesn't touch all that much on Klythie herself, but that's actually because she had a startlingly ordinary early life. She wound up in child protective services as an apparent amnesiac child, and was soon adopted by a kindly older couple. She adapted fairly well to human life, and especially loved having family viewing nights of the Poirot series and reading her parents' collection of Christie's novels. The Costases were the only adults that, after the reveal of the Deep Children's true nature, still fought for their daughter to stay with them. That, in turn, was why Klythie was the only Deep Child that returned to the surface after everything went down. The rest of her siblings were embittered by suddenly becoming exiles from their terrified adoptive families, despised by their older generation of ex-kidnappee biological relatives, and hostages to their governments. Indeed said government was still pretty down on Klythie herself, but once she did some hero work they cautiously allowed her to return, albeit under covert surveillance. She was a semi-unwitting infiltrator the last time, after all.

On the flip side, the monster side of her family doesn't appreciate Klythie's divided loyalties and her making clear that she intends to stay behind when they escape the Earth. That said, they treat her as a still-loved black sheep rather than ostracizing her. There's one important caveat to that though, which is that Klythie's magic is no longer supported by the immense power of "Granny Deep" like that of her siblings. Granny will allow such silliness, but not sponsor it.