The following is a list of the Five Master Guilds and their backstories. Known members of the guilds are provided in bulleted lists, and the leaders of each guild are bolded.
Altosk (アルトスク Arutosuku?), also referred to as Heaven's Arrow (天を射る矢 Ten wo Iruya?), is the most powerful guild in the Union. Led by Don Whitehorse, Altosk serves as primary governing force and maintains order among the other guilds in the Union. The guild frequently represents the Union, such as when the world leaders are gathered to determine a solution to the Adephagos dilemma, and maintain the right to declare war on behalf of the Union. Despite the authorial peace mantra the guilds possess, many guild members show dissent toward the Empire and its ideals. When the Don reads the false letter from Prince Ioder and realizes the letter is inaccurate, he declares war on the Empire merely to appease the guild members. Altosk is highly regarded in respect to the guilds as an entirety. The guild's emblem consists of a bow and arrow, correlating with its alternate name.
Fortune's Market (幸福の市場 Koufuku no Shijou?, "Market of Happiness"), alternatively known in Japan as Guilde de Marshe (ギルド・ド・マルシェ Girudo Do Marushe?), is a merchant guild that focuses on the sales of goods and limited services. With shops located across Terca Lumireis, it possesses the most power in terms of supplies, and its headquarters are stationed in Capua Torim. Mary Kaufman, referred to officially as "Madam President" and often by her surname, is the guild's leader, mandating all services associated with the guild. It is through her influence that the city of Aurnion is constructed on the continent of Hypionia, and she is present in the meeting of the world's leaders during the Adephagos dilemma. She authored the autobiography, Reflections on the Scent of the Sea, which details her life from birth in Torim to becoming a guild master.
Gull's Song is a minor maritime guild associated with Fortune's Market for the sake of transporting goods; Tokunaga, who serves as the Fiertia's captain, is one of its members. The emblem of Gull's Song depicts a ship, referencing the delivery services they provide for Fortune's Market. Members of Fortune's Market are granted travel permits that allow them access to and through restricted areas. The guild's emblem consists of an altar supporting a series of uniform orbs, representing goods and the overall symbolism of trade and balance.
Ruins' Gate (遺構の門「ルーインズゲート」 Ikou no Mon / Ruuinzugeeto?) is an archaeological guild that specializes in excavating blastia from ruins. The guild is highly trusted, despite underhanded dealings throughout the course of the story. Regaey, the guild's leader, is later revealed to be Yeager, leader of the Leviathan's Claw guild. Members of this guild can typically conduct excavations near historical sites, notably the Shaikos Ruins and Baction, and bring their discoveries to Aspio for its scientific citizens to analyze. The guild's emblem consists of an image of a gate encircling an assortment of excavating materials, such as a shovel and pickaxe.
Soul Smiths is a blacksmithing guild that is rarely seen despite its success in the marketing of weapons. The guild's headquarters are forged deep within a mountain, and its members rarely react with others despite its prominence as one of the Five Master Guilds of the Union. According to Nobis Celestial, its leader, the guild has recently fallen on difficult times and requires "Everlight Ore" in order to revive. Galactic Gearbox is a metal-making guild that focuses on selling aesthetic items, such as jewelry. Kale, who was a member of the guild before he died, owned a manual of notes written by Irmine on how to process "Everlight Ore". With this, Nobis effectively used the material to create new weapons and bring the guild back into business. Soul Smiths is one of the few guilds that still utilize the secretive process of guild codes. Yu Seron is the only other stated member of the guild. The guild's emblem consists of a large hammer, a symbol of the guild's work criteria.
- Nobis Celestial
- Yu Seron
Blood Alliance (紅の絆傭兵団「ブラッドアライアンス」 Aka no Ban'youheidan / Buraddoaraiansu?, "Crimson Binds Mercenary Guild") is one of the larger guilds in the Union that consists primarily of an assortment of mercenaries and assassins. Due to their shady actions and secrecy, the guild is highly criticized by others yet frequently hired; Kaufman once employed its guild members to assists in protecting her cargo ships as they traveled across sea. Barbos, the guild's leader, works in junction with Ragou, the magistrate of Capua Nor, and steals blastia cores. Once Barbos is killed at Ghasfarost, the guild steadily declines and is eventually thrown out of the Union altogether. It is later revealed that Barbos sold the former city of Caer Bocram to Alexei Dinoia before the events of the story; Caer Bocram later becomes an unofficial base for the guild. The guild's emblem consists of two opposing axes flipped and facing one another, an ode to the guild's fierce demeanor.