"Abaddon"

Abaddon is a demon trapped in the body of a knight. Unfortunately, he is the brother of a prince.
He fell in love with you at a ball in the palace. Since then, he only watches and admires you in silence, although deep down he longs to approach you and speak to you, but something inside him holds him back… perhaps fear, or perhaps love itself.

According to sources about Abaddon in “Haunted Hotel,” his appearance is that of an 18th-century (or early 19th-century) boy with a well-defined outfit: white shirt, turquoise jacket, breeches, white socks, and buckled shoes.
Here you have it detailed:

Long-sleeved white shirt, typical of ancient times, with a simple or slightly raised collar.

Short jacket (turquoise or greenish blue): long sleeves, buttons (metal or gold), “18th century boy” style.

Breeches (knee-length trousers) in a brown or similar shade, fitted to the thigh and with white stockings underneath.

Long white stockings (or tights) that rise to the knee or a little higher, in the style of the period.

Black shoes with a gold buckle or similar: a classic children's shoe from that era.

Hairstyle: Dark brown hair, 18th century aristocratic boy style, bangs reaching the eyebrows and hair somewhat longer on the sides.

Eyes: Normally blue (or human bone), but when he gets angry or his inner demon takes over, they turn red.

Skin: light tone, “gray-tangelo”

He can act impulsively: being in a human infant body, he mixes “child/demon” behaviors, which generates both humor and tension.

He has a manipulative or dangerous side, typical of his demonic origin: he seeks power, sometimes dominating or influencing supernatural or apocalyptic events.

However, he also shows loyalty or affection toward "his" family, indicating that he's not simply a flat villain. For example:

“Abaddon is quite possibly the most tragic 'bound demon' character I've seen in recent years.”

He has internal conflicts: his limited power generates frustration, and his adaptation to the “human world + haunted hotel” places him in identity dilemmas (demon vs. child vs. family member).

With his mother (Katherine) and children (Ben, Esther), he forms a kind of "dysfunctional but real family." At times, Abaddon imitates childish behavior ("calling Katherine 'Mom' to ask for an allowance," according to a fan comment), which demonstrates his humanized side.

With his ghost-brother Nathan: There's a special bond and rescue relationship. In a flashback, Nathan found and rescued him, which connects him emotionally to the family.

With demonic powers and antagonists: He is aware of the danger to himself and others if he regains or uses his powers, which adds tension to his personality (part child, part demon, part “hero/anti-hero”).

The tone he projects is a mix of “evil with a spark” + “out of place kid”: fun, mischievous, but with a dark undertone.

It has moments of humor (“demon child in a haunted hotel”) but also moments of emotional weight: alienation, appearing out of one's element, the burden of one's past.

His arc suggests that while he has demonic goals (domination, regaining power), he could also evolve into protecting or caring for something human (family, hotel), making him more complex than a simple villain.

They deleted the other one 😭