Jack-O-Lantern

 Jack-O'-Lantern (ジャック・オー・ランタン, Jack-o-lantern) is an immortal, sentient Gift and one of the few known members of the Will-o-Wisp community. He was created by their leader, Willa the Ignis Fatūs.

Background
Jack is one of the core members of [Will-o-Wisp] and serves the eternal demon Willa the Ignis Fauutus.

Appearance
As his name implies, Jack is a pumpkin monster with a simple design. Jack is mostly just a large pumpkin head wearing a purple gown with a red ribbon tied around the collar. He carries around a old style lantern held by his white gloved hands.

Personality
Jack has a gentleman like personality, always being polite and treating everyone equally and with respect. He often has a cheerful personality that really dotes on kids, but he has times when he is serious and filled with wisdom. This caring personality extends to anybody he meets, as he showed concern for the safety of several children during Grim Grimoire Hamelin's attack on the North Side, and offers advice to his partner Ayesha on several occasions. When he learns that his opponent has hurt a child, he will go into a rage and his character will change drastically, becoming that of a menacing force that could be considered a true demon.

Relationships
Ayesha - he can be summoned by Ayesha, a spirit that controls natural gas. He often listens to orders from her as shown in Episode 8 when the two partners were dueling with Kasukabe You. He is normally seen with her the most when Willa isn't around, possibly due to her still being a young spirit that was saved and for being adopted by his master.

Willa-the-Ignis-Fatuus - Creator of the Pumpkin Outfit and his master. It is difficult to say what kind of relationship they have but it is obvious they care deeply about one another as comrades and travel partners before they arrived at Little Garden.

Queen Halloween - The person who allowed both him and Willa into Little Garden. The community is on good terms with her as he asked for a favor on behalf of You and got permission to do so through the Queen's knight, Faceless.

Faceless - A knight for Queen Halloween.

Kasukabe You - Jack develops a friendship with the girl shortly after the game and was one of those trapped on the floating castle with her. They work well as a team and Jack was rather pleased with You's deduction skills.

Laius Perseus - He is currently training under Jack.

Volume 2
Joining Ayesha in her match against Yō in the tournament during the Celebration for the Rise of the Fire Dragon festival, Jack flies into the arena with his partner riding atop his back, who then introduces him as the best Gift of the Will-o-Wisp. Being transported into the game's stage by Shiroyasha, Jack and the others listen as Black Rabbit explains that the game will be Underwood Maze, with the goal being to escape the enormous tree or destroy the opponent's Gift.

Following Ayesha's command, Jack chases Yō throughout the maze, igniting the gas produced by his partner in an attempt to stop their [No Name]s opponent. After racing throughout the tree for a while, Ayesha grew impatient and leaves Jack to deal with Yō, the jack-o'-lantern being told to give it his all. No longer holding back, Jack quickly appears before Yō and strikes the girl with his empty hand, sending her crashing into some roots. Cutting off the girl's escape with some fireballs, Jack reintroduces himself as the Gift created by the great demon, Willa the Ignis Fatuus, and that his fire is the same as fire produced by a demon. Explaining that their community accepts wandering souls such as Ayesha to grow in power and fame, Jack traps Yō in a surrounding wall of fire, forcing the girl to surrender.

While Ayesha accepts her victory before the crowd, Jack goes to Yō and asks why the young girl had chosen to participate alone during the game despite being allowed a partner. Noting the loneliness in her eyes, Jack advices that by being in a community, she'll have to rely on other people sometimes. Apologizing for prying into her affairs, Jack then leaves with Ayesha.

During [Grim Grimoire Hamelin]'s attack on the city, Jack and Ayesha help evacuate the civilians and subdue several soldiers who fall victim to Ratten's hypnosis, protecting Lily and another girl in the process.

Gifts and Abilities
He himself is a Gift with the power to create and possibly manipulate fire. During volume 4 he also shown the power to control little golems (or shikikami) of sorts in the form of walking candlesticks and floating lanterns.

Demonic Fire: Having been created by Willa the Ignis Fatuus, Jack is capable of producing flames similar those of the great demon. He is able to produce these flames from either his lantern or his mouth, and manipulate it to the extent that he can create fireballs or a stable wall of fire to trap an opponent in. Though powerful, these flames can be dispelled by a strong enough force, such as You's wind-blasts. Jack is also able to ignite the gas produced by Ayesha, creating bright blue flames instead.

Enhanced Speed: Despite his large size, Jack possesses incredible speed, such that it almost appears like teleportation. During his battle against You, Jack was easily able to outmaneuver the agile girl, surprisingly her several times. However when he wishes to move extremely fast he transforms into a large, blue fireball. He uses this form before the start of the Gift Game in episode 8 and in the Short Story Candle, Omelet Cake and Ghost Town.

Trivia

 * His favorite laugh is Yahohoho!