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 serves as one of the core members of [Will-o-Wisp] and serves the eternal demon Willa the Ignis Fauutus. One day Ayesha was foud wandering the wolrd and so Jack and Willa took her into their community, with Jack becming Ayesha's partner.

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 - Jack 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 under the service of Queen Halloween. Jack and Faceless are good friends, to the point he uses the nickname created by Willa for her once before, Feisi.

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.

Kudou Asuka - Jack has a respect for Asuka after the way she and Yo performed in the Gift game against [Will-o-Wisp]. Jack considers Asuka a good friend and even revealed his true form in front of her.

Laius Perseus - Jack began training Laius sometime after the Harvest Festival, though their relationship is simply a master and apprentice. Jack doesn't hesitate to greatly injure Laius should he talk badly to his customers.

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.

Volume 3
Jack and Ayesha were at a dormitory when they reunited with the [No Name]s. Jack was thrilled to see Asuka and Yō again and praised them for their efforts in the Gift Game against him. Before he could go on, Asuka quickly interrupted him and learned why it was Jack and Ayesha were in [Underwood]. While he would not be participating in the Gift Game <>, he would be selling the merchandise made from [Will-o-Wisp]. The two groups decided to travel to give their regards to the Hosts of the Festival with Jack expanding about [Underwood] and some of the mechanics involved to make travel easier through the city. When Asuka brought up how the green crystal canals reminded her of a technique from the North, Jack explained that a certain someone from the north brought the technique with them to the south, and that this someone was the same person who helped restore [Underwood].

The two groups met Sala Doltrake, the leader of [One Horn] and main Host for the festival. She brought the two groups to a VIP room and thanked them all for what they did during the [Rise of the Fire Dragon] Festival. Jack told Sala Willa refused to leave the community grounds, much to Sala's disappointment as she wanted to meet the North Side's strongest. When it was mentioned Willa is in the top five digits, Jack mentions that without a community it does not matter. When Black Rabbit excused herself and took her comrades with her, Sala asked Jack and Ayesha to tell them she would like to speak with them later that evening.

That evening Titan's assaulted [Underwood] forcing everyone into a fight. Jack and Ayesha did not participate, and after the battles they were summoned by Sala, along with Jin and Black Rabbit, to discuss the situation. Sala explained how the Titans were remnants of a Former Demon Lord's community and how their objective was an item she had; [The Death Eye of Baldor], which had the power to bring forth elimination, even onto Divine Spirits. Jack was a little skeptical when Sala asked for help guarding the city, especially since his community was more towards blacksmithing than combat. The moment he heard the South Side Floor Master was gone though, Jack had more doubts. The truth of the Festival was revealed, it was a test by Shiroyasha to determine if the [Draco Greif] alliance could rise to the five-digits and take on the role of Southern [Floor Master]. Even when Sala offers the [Death Eye of Baldor] Jack was still reluctant.

Jack and Jin arrived at the medical tents set up after the attack. Jack had let both Black Rabbit and Jin know that Asuka helped out Yō in the Gift Game against [Will-o-Wisp]. A second attack from the Titan's started. When it was learned that Faceless was out at the front lines, both Jack and Ayesha headed off to go assist her, fearing what could happen if Queen Halloween learned that Faceless was dead. The battles ended with [Underwood]'s victory a second time.

The next day Jack offered to lend Yō some assistance in apologizing to Izayoi regarding the destruction of his headphones. Introducing Faceless to Yō, the group was lead ot a ceremony ground prepared to resummon Yō with a set of her dad's headphones. The ceremony ended at nightfall, and while Yō rcovered her dad's headphones, they were not the same as Izayoi's. Jack saw the perplexed expression on Faceless and asked her what went wrong. Faceless took Yō's gift, examined it, and revealed that Yō's power was not just absorbing the power of animals.

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!
 * Jack's origin's trace back to London.