Ruka Feiya

"It’ll be worth the price. Without a doubt."

Ruka Feiya, also known by her pseudonym Jellyfish or her title Harmless King  is a transcendent on the side of the filial duty addicts, set on seeing the world destroyed and learning what happens in the aftermath. She acts as Diarma's successor, taking over his contracts with the humans of Earth after his death.

Appearance
Ruka Feiya's true form is unknown. As an illusion mage, she can alter her appearance at will, and often takes the form of someone dear to the person observing her. When her illusions are scattered, however, she appears as a giant iridescent jellyfish that's hard to look at, seeming hazy and blurred.

Ruka Feiya has a different form used not when manifesting on Earth, but when she's in an unknown space, inside a fog-filled tank. This might be her real appearance. In this body, she retains her long, soft jellyfish tentacles (at least five in number). She also has a chin and a mouth capable of grinning (suggesting that she is at least partially humanoid in appearance), as well as three eyes.

Personality
Ruka Feiya is a cheerful woman, generally straightforward and cordial even with those she considers worthless or below her notice. Though she isn't mindlessly aggressive like Diarma, she can still be distant and cruel, though never dropping her lighthearted attitude. She seems to like making deals, having offered Han Yoojin and others trades at nearly every appearance. She is meticulous, liking to be prepared and know things in advance, and dedicated to seeing things through.

Feiya is not a good actor, or perhaps simply doesn't care about acting out different personalities to match her illusory appearances.

History
Ruka Feiya used to be close to Crescent Moon; the two worked together due to their similar personalities. However, they split apart, possibly due to taking different sides for/against the source.

At some point, Feiya became acquainted with Chatterbox. She was searching through the worlds targeted by the source; though it's unclear what she was searching for, she decided to stop her search at some point before Han Yoojin's regression.

Original timeline, pre-regression
Feiya likely wasn't involved with matters on Earth prior to the regression, since Diarma was alive to take point.

Synopsis
In the new timeline, after Han Yoojin's regression, Ruka Feiya makes her first appearance after Diarma's death at Yoojin's hands. She appears by possessing Yoon Kyeongsoo's dead body, promptly casting an illusion of a more approachable appearance over herself. She explains that she's here to follow up on one of Diarma's existing contracts, and asks Yoojin who Diarma was killed by, though he won't answer her. She attempts to make a deal with him, asking for information, but struggles for something to offer in return. Finally, she settles on a deal where if Yoojin's side can defeat her in one battle (the nature of which is yet to be decided), she will retreat and not interfere with the immoral side's work. Reminding Yoojin to convey the offer to the immoral people themselves, and noting that she can tell he has Diarma's skills, she disappears.

Feiya reappears shortly after in front of Choi Sukwon, the other party in Diarma's surviving contract. She's disappointed by his lack of ability, and orders him to make his guild worthy of her attention within a month. She also gives him an additional offer, allowing him death by "suicide" if he fails his task.

Once that month has almost passed, Feiya returns to speak with Yoojin. She projects herself into his room at Sung Hyunjae's house, disguised as his brother, and offers a new deal. Instead of asking for information in exchange for passivity, she's discovered an interest in him, and asks for Yoojin himself, in exchange for getting Yoojin's loved ones out of the world and to safety. She produces an L-rank contract as she speaks, but the discussion is interrupted by Chirpie physically tackling the contract. Having just noticed it, Feiya becomes strangely focused on it and tries to grab Chirpie, but is smacked away by Yoojin. Sung Hyunjae breaks into the room at his shouting, having been listening outside, and impales Feiya through the stomach with the Seeker's Chains. She's surprised at the connection to Crescent Moon, but is unable to maintain her projection when Sung Hyunjae attacks her again, and disappears.

Two days later, Choi Sukwon goes up against Han Yoohyun and Noah Luire, rejecting his contract with Feiya. This turns him into a beast-like creature of the Harmless Clan i.e. one of Feiya's subordinates. The scene draws attention from all the highest-rank Hunters present, including Sung Hyunjae. When the latter is going with Evelyn Miller to the fight, Feiya blocks their way, shrouding the area in fog, and isolates Sung Hyunjae. She approaches him, disguised as Han Yoojin, and asks about his childhood and relationship to Crescent Moon. Finding that he knows nothing, however, she gives up and leaves.

After Choi Sukwon is killed, Feiya puts the thought of him out of her mind, instead thinking over Yoojin, Sung Hyunjae, and their respective connections to the immoral people. She's surprised that the immoral people chose Yoojin and not Hyunjae as their point of contact, not understanding why. Intrigued, she contacts Chatterbox and asks for his help in managing the current world, tasking him with finding a corpse retrieved by the Bird Who Counts Stars.

The search continues on, with Ruka meeting up with Chatterbox so she can stay updated on his progress and "cheer" him on. Though she doesn't offer him much sincere encouragement, he nonetheless bends to her pleas to keep looking.

Stats
Jellyfish's stat rank is unknown. As a transcendent superior to even the L-rank Diarma, she is likely at least L-rank, though this is not certain.

Skills

 * Unnamed memory-eating fog skill (unknown rank): Possessed as a member of the Fog Sea Clan species. The user can spread an azure fog that swallows the memories of everyone caught in it. These swallowed memories are then converted into raw power and supplied to the user, boosting their abilities. The fog is classified as a poison, and those with Poison Resistance can avoid its effects.
 * Unnamed memory reading skill: Likely possessed as a member of the Fog Sea Clan species. The user can read the memories of others, as well as their emotions; this can be used to find the identities, behavior, and appearances of people they feel friendly towards.
 * Unnamed illusion skill (unknown rank): Allows the user to create illusions that can not only be seen, but also heard and physically interacted with. Multiple illusions can be created on the same spot, appearing different to each onlooker. All illusions seen so far have been centered on the user, acting as disguises, but the skill may also allow external illusions.
 * Unnamed self-projection skill (unknown rank): The user can project themself into different worlds; Ruka Feiya uses this to appear on Earth, combined with her illusion skill to disguise her appearance.
 * Projection is easier with a medium i.e. a person/body through which to channel oneself; for example, Feiya's first appearance was when possessing Yoon Kyeongsoo's dead body. Without a medium, the user's ability is strongly reduced, limiting their ability to cause damage.
 * Projecting into a world runs the risk of rejection from the world. The projection can be made stable by getting the help of someone in the world, presumably through the power of their belief that the user belongs in that world. Ruka Feiya leverages her illusion skill to appear as the loved ones of people around her, satisfying this requirement. The belief can also be strengthened if, for example, the user projects in at a time people are amenable to surreal happenings, such as at night when people are dreaming.

Diarma
Feiya seems to look down on Diarma, describing him as powerful, but dumb, useless, and a failure. She also has the mocking nickname "Yong-Yong" for him, based off the Korean word. Since Diarma never interacted with her in the text, his feelings towards her are unknown.

Crescent Moon
Ruka Feiya and Crescent Moon used to be close, acting as partners. They supposedly had similar personalities, and knew each other's abilities well, able to predict each other's motives. However, they stopped working together and split apart, possibly because Crescent Moon joined the immoral people while Feiya joined the filial duty addicts. Feiya still seems curious about how Crescent Moon is doing and what she's up to, seeking out Sung Hyunjae soon after learning of their connection.

Chatterbox
Feiya seems friendly with Chatterbox. She seeks him out mainly for favors, though doesn't make much effort to speak to him outside of utilitarian reasons. Still, he appears familiar with her goals and motives, so it is possible she is closer to him than things appear.

Han Yoojin
"You’re a rare find, so I’m making a lot of concessions."

Feiya is intrigued by Yoojin due to him being the one chosen by the immoral people. She's willing to go to great lengths to gain power over him and understand what makes him special, but does not appear to be personally interested in him past that.

Sung Hyunjae
"Did you even really have a childhood?"

Feiya is aware of Sung Hyunjae's connection to Crescent Moon, and is curious about why she's given him her powerful weapon, the Refined Seeker's Chains. She seems to know something about his childhood or past, but will not reveal her thoughts to him.

Choi Sukwon
Feiya generally considered Choi Sukwon below her notice, as useless as Diarma. When he was unable to meet her demands to better himself, she treated him as cannon fodder and let him die, forgetting about him soon after.

Trivia

 * She favors worlds with jellyfish or jellyfish-like creatures in them.
 * She seems to like aspects of Earth, mimicking using a smartphone when contacting other transcendents.