Info;

SYNOPSIS
Lord of his subrace (tribe, as they say in-universe), and formerly of the Sarkaz Royal Court as the representative of his subrace-- the Royal Court doesn't officially exist anymore, but he continues to hold the position of Lord of his people. He specializes in the witchcraft of his people, which involves word-based magic, music, the dead, and absorbing the wrath of their ancestors to power up. He also changes 1st person pronouns depending on whether or not he's acting as himself or as the Banshee Lord/Great Banshee, using the regular I for the former and the Royal We (wareware in Japanese) for the latter.
He seems quite strait-laced and a consummate professional, perhaps a little melancholy or impassive because he doesn't emote much. In a way, he is indeed a professional because of his status, and he really doesn't emote much... But that doesn't mean he's emotionless or blank inside, because he tends to have the wildest imagination behind that face-- and likes to act on it. Logos is like a pretentious college student who likes to spout knowledge just because he knows it, and runs off to join in whenever he gets a whiff of a wild-ass party.
BASICS
Canon: Arknights (2D tower defense gacha mobage)
Canon Point: Preferably after Episode 13 of the main story
Name: Aefanyl
Aliases/titles: Logos (codename in Babel and Rhodes Island), Banshee Lord/Banshee Hostess/Great Banshee (changes depending on the language you're reading the lore on)
Age: Unknown, headcanon says mid- to late-20's
Gender: Cismale (he/him), but slightly GNC, can get feminine in appearance and mannerisms, and will not decline any feminine terms of address
Race: Sarkaz (demonic race), specifically Banshee
FIRST IMPRESSIONS
Non-human features: Pointed ears, two small, black-feathered wings on either side of his head, and two long, black stalagmite-like horns on the top of it. One horn is longer than the other and has a branch of its own.
Fashion: Tends to wear a suit as a base, then adds extras like fluttery coats/capes/mantles, long scarves, and trailing sleeves. Leans more towards a techwear style when he's working as a Rhodes Island Operator, but when he acts as the Banshee Lord, he wears a more formal suit with a lot of jewelry and other embellishments. His fashion sense is quite feminine because Banshees are just like that.
Spiritual/magical/aura: His spiritual presence is immense-- he absorbs the wrath of the dead, which gives his aura more weight and can make people assume he's much older than he actually is.
Height: 178cm or approx. 5'10"
Build: Long and lean. He does have a chest because his formal attire shows his cleavage (through mesh, but still).
Hair: Blue-grey
Eyes: Crimson, they glow whenever he uses his Arts/magic
Voice: JP: Fukuyama Jun | EN: Kyle McCarley | CN: Liang Dawei. He's very soft-spoken, which hides just how strong his voice can be.
Language: Likely knows majority or all languages in the world due to his magic relying the spoken, written or typed word. He leans more on Victorian (British English), which is the most commonly-spoken language on Terra, but his native language is Aramaic.
Scent: Like ink, and a bit of ozone due to his constant Arts usage.
Hand dominance: Ambidextrous
Literacy: His magic relies on words, both verbal and written (and electronic), so not only can he read, write and code, but he has a way with words when he must.
Triggers: None. If he does, he refuses to let his emotions get the better of him.
Other: Touching the headwings without permission activates a curse that will knock that person unconscious. Speaking his real name more than three times in quick succession will activate another curse, though we don't know what that does yet. It's like Bloody Mary.

abilities
In general, Terrans are much stronger physically and live longer than Earth humans, and if an individual has cultivated strong Arts/magic, they can live for hundreds of years and retain their youth for most of that time.
Logos is a Banshee and this subrace, or "tribe" as the Sarkaz sort themselves with, tend to be weak physically compared to other Terrans, but with powerful vocal cords to support their Arts and witchcraft-- more on that in the next section. All of them have branch-like horns, and most have functional wings on their heads that they call the Banshee's Crown, which will incapacitate anyone other than their owner if they're touched without consent, though it's unknown if it's enchanted headgear or actually part of their biology.
Originium Arts & witchcraft: Arts is the Terran version of functional magic, readily available to every Terran but not everyone has the talent to train it. It's named after Originium, a Terran mineral that emits its own energy, which Terrans convert into electricity and even magic. Most Sarkaz are talented in using Arts, though they also have their own version of magic called witchcraft, a Sarkaz-only (and offshoots) discipline that predates Originium Arts and makes use of the caster's innate strength as an energy source rather than Originium.
Banshee in particular have their own form of witchcraft, as they specialize in word-based witchcraft and Arts-- basically, anything they say (or sing, or yelL...) happens as long as they add power and intent behind it, and this also extends to anything they write or type. Logos himself likes to hide spells in computer code, as he's comfortable with many different programming languages. As an aside, Logos's name itself has a curse on it, triggered by someone saying it three times or more in 10 seconds, so it's safer to use his Rhodes Island codename. In Sarkaz society, Banshees are known as guardians of the dead and often perform elegies for the recently departed, and on the flipside, taking the wrath of the dead into their bodies to strengthen their power in times of need.
For his individual powers, Logos is a versatile Caster who uses his Arts not just to attack his enemies, but also leave a lasting impression-- every offensive spell he casts has a chance to apply a curse/status effect called Necrosis that damages the enemy over time, slows them down, dampens their strength, and lowers their defenses. He can affect multiple people at once and keep reapplying this as long as he keeps attacking.
For all of his witchcraft and Arts, Logos prefers to use his own personal tool as a conduit-- his bone pen. All Banshee carry a whistle made from bone that they use when honoring the dead, but Logos takes it one step further and uses it as wand, which is capable of writing his incantations in the air before the spell is cast. From the looks of it, it also seems to be capable of acting like a mundane dip pen.
He also has Originium deposits growing inside his body. This is a disease called Oripathy and acts much like cancer, and is a double-edged sword for any afflicted Arts users-- the Originium dust inside someone is capable of acting as an source for Arts, but if someone were to draw on them instead of using an outside source like those who aren't afflicted, they may exacerbate their illness.