Developed by the makers of Riviera (and expanded upon the original GBA version), Yggdra Union takes place in the centrally-located kingdom of Fantajinia. The princess Yggdra Yuril Altowits flees the castle town of Parteena as the nation's era of peace falls apart, the legendary holy sword Grand Centurio in hand. As the only remaining survivor of the royal lineage, she hopes to free her country from its invaders.
Princess Yggdra is the main character of this story, but in the game, you play as Milano, a young boy who leads a group of bandits and ends up meeting Yggdra early on. Battles with the imperial army make up the brunt of gameplay in Yggdra. The game makes use of cards for all areas of gameplay, from movement on the battle field to attacks and parameter changes for your characters. On each turn, you select a card. Players start off with five types of cards, but eventually end up with 30 before the game's end