Keliah's appearance is that of an average tall, slender and voluptuous woman, with her most noticeable feature being the two large gold-looking horns protruding from the sides of her head and pointing upwards. Upon her head is a white band which separates her hair, framing her bangs from her hair below the band. Worn upon her forehead is a small circular symbol with a small dot on the inside and surrounded by several dots around the top. Tied around her neck is a small white-colored strap.
Keliah's attire consists of a very revealing beige-colored leopard-printed kimono, bearing the decorative marks on her shoulders. The kimono is wrapped around her torso with a thick, decorative yellow ribbon that ties behind her back, and her outfit is complemented by thigh-high socks that reveal her heels and toes.
Upon turning her Macro ability onto herself, Keliah is able to force a transformation upon her body by commanding it to go beyond its limits. Keliah changes into a more demonic form than before, with her skin darkening and her horns growing in size. Her hair becomes much wilder, and the clothes around her torso disappears, revealing her bare chest to be covered in an intricate, symmetrical tattoo that begins at the choker around her neck, and ends at her stomach and hips. Her lower body significantly changes, with her legs changing into narrowed stilts that gradually widen up to her hips that now flare out into two wing-like protrusions and her feet changes into those of sharp blades.
Keliah is a calm, stoic, stone-faced Entherious, showing little emotion towards anyone, despite being the leader of her face. Even in her time in the Ryuha Armament Alliance, she emoted very little to her comrades, with the sole exception seemingly being Shuka and Miwa, whom she is very loyal to, if not infatuated with. She displays a calm and calculating persona, never fretting or losing her patience and calmness, taking things with simple steps, as well as take advantage of situations that can prove useful, using others to do so if possible. She commonly uses story motifs in her speeches, though that has become less apparent when addressing people whom she loathes.
Despite being a Entherious and it's leader, Keliah still shows she has hobbies, her primary one being reading books. While she often finds the stories of humans to be boring and even "repetitive", she can acknowledge a good tale when she reads it. Keliah claims she hates the cliche "hero defeats demon and saves damsel"-type story the most, due to having read that type of story many times in her life, and always found it to be boring, even if it wasn't a major part of the grand scheme of things. Her high standarts and taste in literature makes it difficult for her to find a story book she thoroughly enjoys, and would even bother keeping.
She holds pride as an Entherious, which can lead to arrogance, placing the likes of ordinary Demons, humans and Soul Reapers below her and insignificant, refusing to acknowledge a stronger race exists.
Marco: Keliah's special ability, which allows her to fully control control virtually anything, as an act of giving an "order". Said "order" is not always verbal, but can be simply mental. It allows her to control the living, the dead and even inanimate objects with nearly no restraint on what she can do with them. Futhermore, the ability is sometimes mistaken for a type of Telekinesis due to how it causes objects to levitate, or forces movement on others, which is, of course, false. In order to take control of a living being, Keliah must be in the same area, and have eye contact with her target, and from then, she has control. By giving mental orders, she can control anyone from almost any distance, keeping an "order" on them that they must adhere to no matter what gets in their way. However, the only living beings that are confirmed to be 100% immune to the effects of Macro are other Entherious or Demons, or anyone even inherently demonic, hybrids or otherwise. Keliah claims this is due to being of the same species, and that Macro is designed to "control the lesser beings", thus when it comes to other demons, she cannot control them, when they are conscious. If a Demon or Entherious is dead or unconscious, she is capable of controlling their bodies without a problem, but it is not as effective as controlling a living or conscious one.
- Limit Release Removal: After turning her Macro ability upon herself, Keliah is able to enter a form that is akin to the Entherious Form much of her race employs.
- Energy Blasts: Seilah forms kanji circles around her hand, to which a third eye then grows on her open palm. From this point she is capable of generating an enormous blast of energy with enough destructive force to cause a large crater in the Universal Blood War battlefield, and cause enough damage to Mirajane that she was forced out of her Satan Soul: Sitri form, as well as critically damage Sakura, despite the latter's mastery of Medical Ninjutsu to heal her already severe injuries.
- Enhanced Speed: Keliah's speed is augmented to the point of easily surprising Mirajane, despite the Fairy Tail Mage being in her strongest Satan Soul form.
- Flight: With the help of her ability, Keliah is shown to be able to fly at great speeds.
Expert Hand-to-Hand Combatant: Despite her mostly using her Marco for battle, Keliah is shown to possess great skill in unarmed combat and shows a unique fighting style that allows her to swiftly and carefully time her attacks.
Immense Spiritual Power: As a member of the Entherious race as well as it's leader, Keliah boasts tremendous amounts of spiritual energy, well surpassing that of a captain-class combatant.