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Jack's Quest: Demonic Help Party (Jack's くえすと 悪魔お助け隊}?) is a Japanese-only mobile game featuring the Jack Brothers.


Jack's Quest follows in the vein of the Jack Bros. game as a dungeon RPG focused on Jack Frost, Pyro Jack, and Jack Ripper. It was available through a monthly subscription service called Megaten α that offered a variety of Atlus' mobile games and novels related to the franchise.


The game focuses on the Jack Brothers as they attempt to sort out various problems within Makai at the request of the Guild. The gameplay is a combination between the mystery dungeon and rogue-like formats, built on automatically generated dungeons with random item drops. It is displayed with an isometric view. Items, spells, and other demons tied to the series also appear such as Pixie, Alp, Knocker, and Gremlin. By completing quests successfully, a player's ranking within the Guild is raised and they are able to exchange medals for prizes. There is also a shop that offers general items for macca.

Jack Frost learns ice skills and has a weaker offensive ability. Pyro Jack learns fire skills and offers high MP at the cost of lacking HP. Jack Ripper learns force skills and offers high HP and offensive power at the cost of lower MP.

Within a dungeon, player movement and actions are governed by a turn-based system. Attacking enemies from above on the map can increase damage. If a player's HP reaches zero, they'll be ejected from the instance, losing all items, macca, magnetite, and summoned demons. Their level will also be reduced to 1. HP recovers slightly every turn and it is possible to acquire healing skills and items. Additional spells in particular can be obtained by items dropped within the dungeon.

Magnetite within the game is treated as a demon's energy and it decreases with each turn passed, starting from 100. Once it is completely depleted, it will gradually reduce the player's HP. It can be acquired through demon negotiation and replenishing squares. The negotiation process is done through Kotodama, which can be acquired through medal turn-ins and treasure chests. In successful negotiations, players can receive an address from a demon. Addresses allow the player to call demons through the Devil Phone. Demons acquired through this process can join the player in fighting in dungeons, though they require magnetite as a maintenance cost.

The Moon Phase System also effects how the dungeon functions. Full Moon disables the Devil Phone and prevents negotiations. The New Moon makes item usage impossible.


  • The game was initially announced via NTT Docomo as "Jack's Dungeon", this title was simply a placeholder and was changed before release.

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