Infinite Undiscovery is meant to envelop the player in a real-time world where individual decisions can unveil numerous discoveries and affect other encounters, without the need to transition to another screen and can occur at anytime, even while the player is going through inventory in the menu. An action based battle system allows up to 4 characters that can be on the field at once is used. The player controls the main character Capell from a third-person perspective while the other 3 characters are controlled by AI, however using connect actions Capell can use another character's skill. Faced with a variety of episodic situational battles, the player is meant to try various methods to defeat the enemy, where the most obvious solution is rarely the right move. Certain battles require the player to divide the whole of the cast (said to be up to eighteen characters) into teams due to the sheer size of the situation. Infinite Undiscovery will feature a "multiparty" system, allowing the player to divide his or her allies up between a possible 3 groups of 4 members each. Since Capell is the only "fully" playable character in the game, the party lead by him is known as the "main party" while the other two are classified as "sub parties." There will be times when all three parties will participate in the same mission, all being present on the battlefield.
It is important to consider the personalities of each character that you put in each party, as they will act differently based on who they are working with and the personality of that party's leader. It also appears that characters' personalities may change once certain criteria are met.
There is a phenomenon known as Lunar Rain - power from the moon falling down to the Earth, granting those who are touched by it better stamina and more power to their glyphs, more formally known as Lunagrams. Since the Order of Chains chained the moon, the Lunar Rain falls almost exclusively on the Halgeetah region. For some reason, Capell does not feel comfortable in the Lunar Rain.
The game transitions between day and night about every 10 minutes and the player must use this to their advantage. For instance, at night the player might have a better chance of infiltrating an enemy base stealthily as opposed to barging in during the day. Light stealth elements like this are hidden throughout the game, director Hiroshi Ogawa explains: "As an example, when you’re running away from a hunting dog, you can distract him by dropping apples from the trees. However, the guards may catch you when they hear the thud of the apples."
Infinite Undiscovery takes place in a world where the Dreadknight Leonid and his Order of Chains, binds the world to the Moon from all regions. The Main chain being in the fallen Kingdom of Cassandra (formerly King Volsung's kingdom) and attached to the Castle - Leonid's HQ. Any region with a Chain, suffers it's consequences. Crops wither, and animals die, thus Sigmund the Liberator goes forth with his Liberation Force to unchain the world; But Capell is thrown into this for which he wants no responsibility of. Inevitably, these chain of events will changed his life and those around him forever...
Most characters in Infinite Undiscovery are born with glyphs, symbols on their skin that grant them magical powers. Capell is the only character who is known to lack a glyph.
- Capell - A flutist that is mistaken for Sigmund the Liberator and is imprisoned by the Order of Chains. Lacking the qualities of a hero, even his captors doubt his identity. Although he wants to remain uninvolved in the turbulent events surrounding him, it seems fate has something planned for this reluctant hero. Capell is a Glyphbare(Unblessed), a person who lacks a symbol most humans have on their bodies. This is due to him being born during the new moon and is considered cursed because of it. He was abandoned as an infant, but raised by a troupe of minstrels. However, Capell has had to endure hardship and persecution because of his lack of a glyph. Capell tries to hide his secret of being "unblessed" from his fellow comrades. Despite never having wielded a blade, Capell quickly starts to master swordsmanship.
- Aya - After Capell is tossed in prison, she rescues him, thinking that he is Sigmund the Liberator. However, after a short while she realizes Capell isn't Sigmund, but rather a minstrel who bears an uncanny resemblance to him. She has fought alongside Sigmund and fully places her trust in him. After getting to know Capell, she begins to become attracted to his quiet strength and kind heart. She wields a bow that she augments with her fire glyph, resulting in explosive arrows. By connecting with Aya, the player is able to aim and fire her bow. Aya Also turns out to be a princess, next inline as the "Emir" in her country.
- Sigmund - Better known as the Liberator. He is the only one with the ability to break the chains that bind the moon, hence the title. Lord Sigmund was raised like a son by the Empress of Halgita, Svala.
- Edward - A cool headed man who wields a large sword. He is the same age as Capell and Sigmund and is a loyal follower of the latter. Though normally cool-headed, his anger can get the best of him and he is growing jealous of Sigmund's trust in Capell. Lord Sigmund saved Edwards life and has devoted his life in return. Later through the game, Capell (in a likewise near death experience) saves Edward's life, and pulls him from the brink. Edward realises something and respects Capell from there on in.
- Rico - One of the young spell-casting twins, one male and one female. He is a beast tamer. By connecting with him, the player can talk to animals.
- Rucha - She is the female child of the young spell-casting twins. She is a summoner. Her connect action is Scavenger, which allows the player to obtain one item from another while leaving the latter intact, allowing the player to get two items from one.
- Michelle - A seductive looking woman who uses books to cast spells and is a healer. She mistakes Capell as Sigmund as well as claiming to be Sigmund's lover. After hearing of Capell's childhood, she declares that she will be his sister. She usually moves at her own pace and comes across as a bit of a bimbo. She is a big fan of tea and always has a kettle and cup ready. Her Japanese name is Mirche.
- Komachi - A beautiful female ninja who wields twin kodachi and uses magic. She is also shown to use giant versions of shurikens, similar to Yuffie Kisaragi of the Final Fantasy series, developed by Squaresoft (before merging to form Square-Enix). She has a unusual hairstyle, in that instead of her hair being tied with a bow, she uses her hair in place of a bow.
- Eugene - A knowledgeable looking man, he uses a staff in battle. He is a friend of Sigmund and the heir to a wealthy merchant family. Though a kind man, he does have a dark side. It is unknown what is in the huge backpack he carries.
- Balbagan - A large man who wields a battle axe, he accompanies the liberation army to have a rematch with Sigmund, to whom he once lost in a duel. He is a rather simple-minded man, often leaving the thinking to others and spends his time napping or eating. He is the oldest of the party at thirty-five.
- Touma - A white-haired youth who wears a Japanese fox mask and wields a katana that appears to become a laser sword. He is a young aristocrat whose family has served the empress of Halgita for years. His family also controls an elite group of warrior spies called the Nightwhisper Guild. He is an old friend of Sigmund's and is one of the few people who knows his past. Though his actions are dignified and just, he is a tad naive.
- Gustav - A giant red bear with a single horn growing from his forehead. He is actually Aya's pet who she has kept for years. He believes Aya to be his mother and protects her fervently, which prevents him from getting along with other members of the army (especially Capell). Judging from trailers, Capell can ride on Gustav's back.
- Vik - A young boy with rather prominent freckles on his face. He is shown to wield knives, and appears to be rather mischievous. He wears a bandaid over his nose, and a exposed naval. He is actually a girl.
- Sorenstam - A green-haired man who wields magic. His ears appear to be pointed.
- Kiriya - Another wizard with extremely long, blond hair. His clothes resemble Japanese garments. He is shown to have very effiminate poses and mannerisms. He appears to use some sort of flail, and a blade like weapon, similar to a hook.
- Subaru - A blond-haired woman who is of unknown age. She is shown to hold a fan.
- Faina - A teenage girl who falls inlove with Capell after he saves their village. Like Capell, Faina is a "Unblessed". Born without a glyph.
- Leif - Faina's younger brother.
- Leonid - The man who enslaved the moon with chains. He is a Dreadknight and created the Order of Chains. Later it is revealed when the player reaches Kolton after a series of events, that Leonid is in fact Empress Svala's son. She then pleads with Capell to stop him, knowing that Leonid is to far into what he has done to be saved.
- Saranda - A seductive, red-haired woman who wears a elaborate dress the same color as her hair. She is shown to be an ally of Leonid's and wields a blood-red chain-whip.
Infinite Undiscovery was announced in September 2006 via Famitsu. Initially it was believed that Microsoft would publish the game, however at TGS 2007 Hajime Kojima and Hiroshi Ogawa stated that Square-Enix took over publishing duties because they have more "know-how" with RPGs. However, since Microsoft was the original publisher, they still hold the intellectual property rights to Infinite Undiscovery.