I'm sure this has been pointed out before, but couldn't she be the daughter of Alva and Zullie? All the spells that she sells you (the ones SHE has, not the ones she sells you after you give her tomes) are "passed from mother to daughter", the item description of Karla's pointed hat states that "pointed hats are the signature of a heretical sorceress (specifically points towards an individual, most likely Zullie IMO)" and if you read the item description of Zullie's black witch hat it says "The pointed hat is a symbol of heretical magical crafts, and Zullie wore hers with an unspoken, but deep sense of pride.". I take from this that Karla learned the spells she has from her mother and that she wears her pointed hat as a kind of nod towards a specific sorceress, Zullie also happens to wear a pointed hat and "takes great pride" in her hat so it makes sense to me that if she was teaching her daughter black magic that she'd want her to wear a pointed hat as well since pointed hats are "a symbol of heretical magical crafts" as told to us by Zullie's black witch hat item description. It's also possible that the reason Karla wears a pointed hat is because Zullie (may have?) killed herself, it's a nod to her dead mother. If you read the item description of the spell Dark Edge, it says "Passed from mother to daughter, this blade was intended for both protection and as a means of taking one's own life. The young girl never swung it more than once." which could imply that her mother only cast the spell once to teach her how to use it, hence her only using it once as she no longer had any point of reference to practice on. Her mother may have brought Karla near her during the suicide and "taught" her the spell by committing suicide and then Karla attempted the spell once right after her mother died either to try to kill herself as well or just to attempt the spell that her mother died to teach her. All of the above information ties Karla to Zullie, but doesn't really cover Alva, i'll try and move on to him. First things first, Alva invades right outside the Irithyll dungeons and is later found dead near Karla's cell. Alva is titled "seeker of the spurned" in dark souls 3, Karla references to herself as a "spurned child of the abyss". We can gather from all this that Alva's invasion isn't coincidental, he was in the dungeons trying to find Karla, whether it's because she's his daughter or just because she is considered "spurned". We know he was specifically there for Karla because his corpse is near her cell as mentioned above. Alva ALSO invades in front of the corpse that you get Zullie's black witch set from. We already know from the item description of Alva's set and Zullie's set in dark souls 2 that Alva and Zullie became close either during Alva's quest to find a cure for saint seretta or after she died of said sickness. The item descriptions are as follows: Alva's set: "Alva crossed many a land in search of a cure for Saint Serreta's sickness, but failed and relinquished his knighthood. Alva was once wracked with guilt and remorse, but rediscovered his purpose in life with the aid of the witch who once plotted against him." Zullie's set: "Robe worn by Zullie the witch,seducer of Alva of Wayfarer. Boasts excellent magic defense. When Zullie the witch learned of Alva's dedication to Saint Serrate she used all manner of tricks and deceit to ruin him, but in the end she would spend her life with him, supporting his endeavors. The witch, as unloving as she was unloved, finally found illumination through her blighted existence." From these item descriptions its undeniable that they became AT LEAST very good friends, but i believe they became lovers. Alva's ENTIRE purpose in life prior to Zullie was to save a saint dying of an incurable disease, he even travelled around the world enough that tales about his exploits and his involvement with the witch earned him the title "the wayfarer" to those who spread the tales. His motivation was enormous, enough that when he failed he relinquished his knighthood as punishment. The fact that a woman who is titled as "SEDUCER of Alva" became a big enough presence in Alva's life that she was able to help him move past this failure and live on alongside her implies, to me, that he fell in love with her. The black witch veil MIGHT point towards them having gotten married at some point, but it's explained in the item description as "for travel and to hide her affiliation with the misunderstood craft of witches" so there is already an explanation for it aside from "they got married". It's just something to keep in mind. At some point Alva and Zullie were split up, it is shown in the ringed city dlc that she ended up working under the judicator giant and as we see through our playthrough, Alva is shown watching over Zullie's (possible?) corpse in the ringed city and seeking Karla in the Irithyll dungeons. We can easily understand why he's looking over Zullie's corpse, she meant EVERYTHING to him after Seretta died (it literally says that they "found a new purpose in life in each other), but why would he be seeking Karla? Well, if you've read through everything i've said so far you'll have noticed that i've already pointed out that its highly likely that Alva and Zullie weren't JUST friends, that everything in Karla's possessions indicate that her mother was dark sorceress and that her pointed hat is a connection to Zullie. Given all of this together it is likely that Zullie is Karla's mother given that all of Karla's spells are "passed from mother to daughter", as far as Zullie killing herself, as i mentioned earlier Alva and Zullie were split up at some point. What I believe happened is that they had a child (Karla) and then were split up in the ringed city by circumstance so Zullie raised their daughter as long as she could all the while teaching her daughter her dark arts and holding out hope Alva would find them again. It is once she has taught her daughter all but one spell, dark edge, that she finally loses hope of Alva being alive and as such decides to kill herself, in the process passing on her last dark art to her daughter. Karla grows up and is imprisoned in Irithyll dungeons because of her black magic, ages pass with Alva still away searching for both Zullie and his daughter when he finally finds Zullie's corpse in the ringed city, grieving her he protects her corpse until you come and take her items, Alva then goes in search of his daughter and hears of her having been imprisoned, he rushes to the dungeons and sees you coming towards the dungeons so he fights you in an effort to protect his daughter from you since for what OTHER reason would a powerful person like yourself be approaching a dungeon other than to cause havoc, you beat him but don't kill him so he proceeds as far into the dungeon as he can get until he is later killed by the jailers keeping watch down near Karla's cell. I'm on the verge of tears right now, because the reality JUST hit me while i was typing this, its all coming together for me and i don't like the picture. Please, someone prove me wrong, seriously.