Jack Skellington

Background
While his origins remain unknown, it is known that some millennia ago Jack took a liking to Earth and swore to protect it from invasion by otherworldly threats. Over the centuries, he has gained a fearsome reputation within the monster community of Earth for his ferocity in protecting humans. This reputation is so strong that he inspires fear among undeniably good monsters, such as Mavis Dracula.

At some point, Jack acquired some "history" with North of the Guardians and forged strong ties with the team. Through them he met Rebecca "PH" Windwalker. He was apparently on good terms with the teams then-leader, the Sorcerer Supreme Moon Man, whom Jack describes as "shining like the moon".

Centuries in the past, Jack apparently had interactions with a Celtic Princess. While the nature of their interactions remains unknown, he apparently considered her a friend. He also owed her a debt, though how this came about remains unknown.

Several decades before the series, Jack confronted and dueled an entity known as the Beldam, a creature who fed on the souls of human children. He fought her with ease and burned out her eyes, leaving her alive and trapped in her own realm.

Personality
Despite his ancient and undead nature, as well as his immense power, Jack is a pleasant and amiable entity, with a strong sense of humor and affable demeanor. Jack has a strong sense of honor, as shown during the Dark Spirits Incident, in which he told Archer that "his debt had been repaid". He is a natural showman, as shown when fighting with spectators he tends to "go all out".

Jack is a self-described "gentleman", with a strong courtesy toward women and wide chivalrous streak. This goes so far as to spare female opponents, though not without severe injury to prove that he will not hesitate to kill them for a second offense. Jack favors humanity, seeing the good inside them, and chooses to use his immense power to protect them from extra-dimensional threats.

Jack is a good and caring friend, as evidenced by his friendship with such heroes as North of the Guardians and Rebecca "PH" Windwalker. He seems to have little regard for formailty with close friends, such as PH. He is also quite loving and respectful to his romantic partner, Sally Finkelstein. He has shown a tendency to place the happiness of his loved ones above his own desires, as evidenced bu his opinion of his cousin's spouse.

However, when facing an opponent, Jack's demeanor takes a complete turn from usual, hardening into a merciless, brutal fighter. Though never unnecessarily cruel, Jack is pragmatic and fierce in combat, destroying his opponents with decisive force. His fearsome tactics and immense power have reflected in his reputation throughout the realms, further solidifying his role as a defender of humanity.

Appearance
Though not human, Jack's natural form resembles a tall male skeleton with bleached-white bones, wide shoulders, large hands, and seemingly-small feet. He dresses in a black pin-striped suit and black bat bow-tie.

When in his "Pumpkin King" guise, Jack appears as a burning scarecrow with a Jack-o-Lantern for a head, a fearsome face carved as his expression and dressed in rags. Flames emanate from the Jack-o-Lantern, further adding to it's fearsome appearance.

Powers & Abilities
Jack Skellington is an incredibly powerful individual, with power described as rivaled only by a Sorcerer Supreme. He has showcased his power by defeating monsters and entities considered extremely powerful by humans with almost casual ease. His reputation is so fearsome that monsters all through the realms fear his retribution.

As an ancient extra-dimensional entity, Jack possesses numerous powers and abilities. These include:
 * Immortality: Jack is ageless, having lived for several millennia at the very least. Unless killed, he will likely live forever.
 * Superhuman Strength: Jack possesses exceptional superhuman strength, derived from his undead and inhuman nature. Jack has displayed sufficient physical strength to jerk a ghoul-king the size of a two-story house bodily into the air, whirl it above his body, and slam him back into the ground. He can likely bolster his strength with dark energy, though his natural strength levels remain unknown.
 * Superhuman Agility: Jack is capable of moving with more speed and grace than humanly possible, allowing him to fluidly move and dodge the attacks of others with little effort. He is capable of jumping the height of several stories and contorting his body into inhuman positions. He is also capable of reacting with inhuman speed.
 * Invulnerability: Despite being attacked by countless powerful monsters and demons, Jack has sustained no permanent damage. His undead nature and incredible power allow him to shrug off most, if not all, forms of attack.
 * Pyrokinesis: Jack has displayed the ability to summon and control incredibly powerful supernatural flames, capable of easily destroying monsters and harming spirits. There appears to be no limit to the amounts of flames he can summon, as he has seared away an entire pocket dimension full of dark spirits. He also seems to be able to control whom his flames burn, as Night Fury and Archer remained unaffected during this incident.
 * Shape-Shifting (limited): Jack can take on his "Pumpkin King" form, resembling a flaming scarecrow with a Jack-o-Lantern for a head. He seems to prefer this form when using his pyrokinesis. Whether it enhances his powers or is simply a psychological tactic remains unclear.
 * Dark Energy Absorption: Jack is capable of absorbing the arcane energies of monsters he has killed, with which he can boost his innate powers.
 * Martial Prowess: Jack has displayed a unique and highly effective style of combat, honed and perfected over his millennia of fighting, that takes full advantage of his supernatural strength, agility, and the Soul Robber. His marital style has been likened to dancing, incorporating graceful leaps, spins, and twirls that dazzle onlookers and confuse opponents.

Equipment

 * Soul Robber: As a weapon, Jack utilizes a unique object known as the Soul Robber, appearing to be composed of green slime. In addition to obeying its owner's commands, the Soul Robber is capable of stretching itself to indeterminate lengths and altering its shape to suit its wielder's needs, such as forming a whip, a harpoon, or a sickle.
 * Skeleton Key: Jack possesses a powerful mystic artifact know as the Skeleton Key, appearing as a large, intricate, bone-white key. This object allows him to open portals to access and traverse between any dimension or realm in existence. it can also permanently seal crevices and openings between realms, preventing others from leaving.

Titles
As a powerful entity known throughout the realms, Jack has accumulated numerous titles of respect.
 * King of the Pumpkin Patch (often shortened to "Pumpkin King")
 * True Master of Fire and Fear
 * Lord of Darkness
 * Spirit of Halloween
 * Monster That All Monsters Fear