An updated version with bonus features was released in Japan for mobile platforms and Nintendo Switch in April 2019 and March 2020, respectively.

Each unit comes with six stats: Morale, an indicator with a function similar to Hit points; GEN, generalcy; ATK, attack; TEC, technique; and LUK, luck.

Each unit also has the potential for five 'effects', which are strategy altering hooks that do many things, from the in-clash voiding of damage enhanced with a particular element, to out of clash Morale restoration.

Throughout the story, the idea that justice lies with the Holy Sword[1] is used to drive Yggdra and her army forward through their plight, as well as to provide explanation to them for the acts they commit.

The story mainly details Yggdra's reclamation of her kingdom from the Bronquian Empire, and her eventual uniting of the entire world under her sovereignty, with quite a few stops along the way leading to an intricate and involving plot.

Heaven universe and story, deeply tying the game into mythological elements first developed by Riviera, with the more direct appearance of Diviners, and Grim Angels, and passing mention of Malice, Hector and The Seven Magi.

The lead male of the story is Milanor, the seventeen-year-old[2] thief king; The Silver Wolf, whose home was burned down by the Empire in an attempt to find Yggdra.

Nietzsche, the twelve-year-old,[2] naïve Undine from Embellia joins the Royal Army to gain revenge on the Empire for their espionage in her country, as well as to search for the Transmigragem.

Twenty-one-year-old[2] Necromancer Roswell of the Branthese house and nineteen-year-old[2] Witch Rosary of the Esmeralda house are met in Verlaine Hills, one of which will join the Royal Army for revenge on the Empire's involvement and betrayal in Verlaine and to recover the Ankhs, the other of which will die at the hands of the Royal Army.

Kylier is a seventeen-year-old[2] Griffon Rider from Lost Aries, with an affection for Milanor, who never really joins the Royal Army, but assists them when they need help most.

Cruz is a twenty-two-year-old[2] hunter, who made it to number one on the Empire's Most Wanted List for his leadership of the Karona Resistance and joins the Royal Army after his headquarters is tracked down and attacked by Mizer.

A descendant of Brongaa, and seeker of his resurrection, Gulcasa took the Empire in a violent coup d'état, and immediately began conquering neighboring countries.

Leon is the first introduced of the five Dragon Generals, twenty-two-year-old[5] brother to Elena, he is called the Black Knight for his excessively wanton violence and cruelty.

Eudy, the twenty-eight-year-old[5] Court Magician, is another high ranking general in the Imperial army, and the cause of many cannon woes.

[9] The PSP version, also initially revealed by Famitsu and soon after confirmed by Sting, was given many new features, including completely redrawn sprites and new characters,[11] as well as modified game mechanics such as increased unit capacity, and an animated opening cutscene previewed on the development blog.

[12] Other changes include new story sequences following one of the endings of the game, returning character Pamela as playable, a hard mode, new status effects attached to several skills, as well as new cards and battlefields.

A remastered version featuring various quality-of-life adjustments, including an easier difficulty setting and battle speed options, was released for Android and iOS on April 11, 2019, and for Nintendo Switch on March 5, 2020, both exclusive to Japan.

The full release, planned for later 2023, only aims to fix found bugs and improve the experience based on player feedback.

[15] Following the surprising success of Riviera: The Promised Land,[7][8][16][17] Atlus USA was quick to take the opportunity to end "on a high" on the GBA by localizing Yggdra Union.

[8][18][19] This decision caused the release to be pushed back as Atlus USA announced more GBA games such as Summon Night: Swordcraft Story and Super Robot Taisen: Original Generation.

Nich Maragos, lead editor in the localization effort, notes such difficulties as the extreme text constraints, as well as Atlus USA's busy release lineup leaving Yggdra Union short on staff.

[22] Aside from physical merchandise, Sting has also released a large amount of Yggdra Union download content for their mobile service Sting Station (スティング☆ステーション, sutingu suteeshon), such as calendars and wallpapers featuring artwork from the game, ringtones based on soundtrack themes, and even several games that can be downloaded and played.

Yggdra Union has an extensive soundtrack, totaling nearly sixty tracks[26] co-composed by Shigeki Hayashi and Minako Adachi.

[22] Aside from the music, the audio in the GBA version of Yggdra Union is fairly standard, with sound effects in battle and beeping for text of a pitch based on the character speaking.

[44][45] In Japan, the GBA version tied in fortieth place in Famitsu's Reader's Top 100 Games of 2006[46] and was given a score of one nine, one ten, and two eights, for a total of 35 out of 40.

[47] Despite this, when Yggdra Union was released in Japan, GBA sales saw a noticeable spike, a potential correlation noted by GamesAreFun.

In battle, characters move around in real time, and when two opposing enemies encounter each other, a skirmish more similar to those found in Fire Emblem is initiated, with the units attacking each other.

JaJa's blog had featured discussion and photos of Yggdra Unison (code-named "YZ") for several months before the official announcement.