Players guide their party of adventurers through the town of Zey Meruze which acts as a central hub and five different areas called Alterworlds, acting as the dungeons. In order to progress through the game, players must undertake quests which are obtained from the Raiders Guild in town. This system is a departure from previous games in the series, and allows players to undertake multiple tasks at once and to choose their own way through the game to an extent. As tasks are completed, the party gains guild points. Once enough guild points are gained for the next rank, the next part of the main plotline follows, before more side-quests in the form of tasks are made available.
When the party moves from the town to an alterworld to complete a task, a timer starts counting down. If the task is not completed before the timer runs out, the party is safely removed from the alterworld and must attempt the quest again.
Alchemy forms an important aspect of the story and gameplay, as with the other Atelier Iris games. Items are combined in the party's workshop by the character Iris, forming new items and equipment. This system is used to create attack items for combat, healing items, status attack or restoration items, weapons and armor for characters to equip and various other items.
The game also features some side story characteristics, that allow Edge to engage in conversations with some of the townspeople upon the completion of certain quests. These conversations provide additional details about the townspeople.
Unlike previous games in the series, the maximum number of playable characters is 3. However to compensate for the fewer number of characters, once a certain point is reached in the game, Edge and Nell can equip various "Blades" which can change their combat style and skills.Edge Vanhite (エッジ・ヴァンハイト, Ejji Vanhaito)
Voiced by: Nozomu Sasaki (Japanese); Vic Mignogna (English)
The male main character, aged 19, who works as a Raider exploring the Alterworlds. After losing his family at a young age, he has since been living with Iris. He's quiet and his honest personality makes him seem unfriendly but deep down is kind and sensible at heart. He is also revealed to have romantic feelings for Iris.
Iris Fortner (イリス・フォルトナー, Irisu Forutonā)
Voiced by: Miyu Matsuki (Japanese); Michelle Ruff (English)
The female main character, aged 16, who works with Edge as a Raider. Growing up in an alchemist family, she can do simple synthesis. She has an optimistic and straightforward personality but is a little clumsy. She shares a namesake with Iris Blanchimont from Atelier Iris and Atelier Iris 2, but aside from similar looks, the two are completely unrelated.
Nell Ellis (ネル・エルエス, Neru Eruesu)
Voiced by: Natsumi Yanase (Japanese); Jessica Straus (English)
The third playable character, aged 15, who works with her older sister Yula as a Raider to rebuild their family wealth. A very energetic girl often lacking seriousness. After getting into a fight with her sister, she joins the party in Chapter 3.
Ash F. Abenstein (アッシュ・フォン・アーベンスタイン, Asshu Fon Ābensutain)
Voiced by: Daiki Matsubayashi (Japanese); Kirk Thornton (English)
The highest ranked Raider in the world, who always works alone.
Annastra (Anna) Servatika (アナストラ・セルヴァティカ, Anasutora Seruvatika)
Voiced by: Junko Ueda (Japanese); ? (English)
A Guild receptionist, who handles normal quests. A shy and gentle person, she always gives a warm and friendly "Good work." to every Raider at the completion of their quests.
Phenyl Neet (フェニル・ニート, Feniru Ni-to)
Voiced by: Sayaka Narita (Japanese); Sandy Fox (English)
A Guild receptionist, aged 12, who handles combat quests. Phenyl is a rude and unfriendly person, who has a bit of a complex about her height: she takes extreme offense at comments made about it.
Ewan Kleines (ユアン・クライネス, Yuan Kurainesu)
Voiced by: Satoshi Katôgi (Japanese); Patrick Seitz (English)
A womanizing researcher who works at the Scripture Library. Ewan is an intelligent person, but his carefree and narcissistic attitude never makes him seem that way.
Yula Ellis (ユラ・エルエス, Yura Eruesu)
Voiced by: Hazuki Nishikawa (Japanese); Wendee Lee (English)
A daughter of a wealthy family. Yula comes to Zey Meruze with Nell to work as a Raider in order to rebuild their family wealth.
Alvero Kronie (バージゼル・クローネ, Bājizeru Kurōne)
Voiced by: Tetsuya Kakihara (Japanese); Derek Stephen Prince (English)
An overly proud Raider, of below-average skill.
Noella Martyr (ノエイラ・マーテル, Noeira Māteru)
Voiced by: Miwa Kôzuki (Japanese); ? (English)
The Guild Master. Once a highly ranked Raider herself, she is optimistic person who often smiles despite her busy work schedule.
Kremeyna (Meyna) Neju (クルメーナ・ネジュ, Kurumēna Neju)
A retired female Raider who is always seen standing sadly at the memorial stone and says very few words.
Pamela Ibis (パメラ・イービス, Pamera Ībisu)
A ghost librarian in Grimoire Castle. She has a bubbly personality, but is painfully forgetful. She also has a rather amusing habit of appearing in front of people out of thin air, sometimes resulting in her scaring the bejeezus out of them. Pamela is a recurring character in the Atelier series.
Crowley (クロウリー, Kurourī)
Voiced by: Kunihiro Kawamoto (Japanese); Derek Stephen Prince (English)
A mysterious ex-Raider who currently hires other Raiders for his own secret agenda.
Manna Martyr (マーナ・マーテル, Māna Māteru)
Voiced by: ? (Japanese); Sandy Fox (English)
Owner of the Grocery Store. Manna is a hard worker with a bright smile, but she has a slow personality.
Ella Fulchaphen (エラ・フルクハーフェン, Era Furukuhāfen)
Voiced by: ? (Japanese); Wendee Lee (English)
The bookstore owner. Ella is bored of her job, and is unfriendly to her customers. She is a childhood friend of Iris.
Yacht (ヨー・ヤッケ, Yō Yakke)
Owner of the General Store. A merchant from a faraway land who loves rare items who has a bit of a greedy personality. Yach also appeared previously in Atelier Iris 2: The Azoth of Destiny
and Atelier Iris: Eternal Mana
, but it is unknown if they are the same people.
Hagel Boldness (ハゲル・ボールドネス, Hageru Bōrudonesu)
Voiced by: ? (Japanese); Kirk Thornton (English)
The owner of the weapon store who is passionate about weapons whose only concern is his bald head. Hagel is a fixture in many of Gust's works, appearing in both previous Atelier Iris
games as well as Ar tonelico
Funan :A fisherman with a philosophical personality about fish.
Plua: The DARKNESS Mana, found deep within the confines of Grimoire Castle. The Elder demon controls her and turns into an Elder Dragon as her second form to defend against Edge and company. When acquiring Plua, she sends enemies into deep slumber and allows Edge the ASSASSIN BLAZE—specializes in speed and high evasion bonuses.
Nymph: The WATER Mana, possessed by an Ice Sprite in the Posporia Fairyland lake region. When released from the Ice Sprite, Nymph launches a giant ice wall onto enemies for ice-damage and allows Nell the SAGE BLAZE—specializes in healing and support skills for curative purpose.
Siren: The SOUND Mana, who can be optionally found near the fishing area of Ishtar's Woofer promontory. The demons, Musica and Cancion, guard Siren; when freed, she blows a tuba to divide enemies HP 25-50% off, allowing Nell the ANIMAL BLAZE—specializes in many Kobold assistance and speed bonuses.
Jiptus: The POISON Mana, that can be found in the marsh area of Valtessa Forest. When Edge liberates Jiptus, she stings one enemy to lower POWER/SPIRIT, allowing Edge the DEAD BLAZE—specializes in summoning dark friends and high anti-dark attack bonuses.
Diemia: The STONE Mana, found in the Stone Sanctuary of the Posporia Kuma Fort area. Once freed, Deimia charges at enemies in a straight line for stone-damage; allows Nell the FORTIFIED BLAZE—specializes in high-physical attack upgrades equal to/greater than Edge with a larger rapier.
Fanatos: The EVIL Mana, trapped within the Squawks Magic Castle. The summon uses a shocking trident on one enemy for lightning-damage, also allows Edge the MARTYR BLAZE—specializes in all upgrades (minus speed) with the ability to AUTO-REVIVE.
Faustus: The ILLUSION Mana, sealed in the Crystal Rookery of the Dakascus's crystalline Pengie Tribe. Faustus nullifies all status upgrades of one enemy and allows Nell the TOYMASTER BLAZE—specializes in using dolls, but very slow with high defense bonuses.
The TIME Mana, who can be optionally unsealed by seeking the Shadow Stalker in Ishtar's Uroborus Seal area. The Shadow Stalker is the most difficult boss but when destroyed, Luplus casts HASTE on the party, also allows Edge the CHRONOMANCER BLAZE—specializes in high-arcane magic attack upgrades using ancient tomes.
The soundtrack was mainly composed by Ken Nakagawa with the opening song composed by Revo and two other vocal songs composed by Daisuke Achiwa. It was released June 21, 2006 in Japan by TEAM Entertainment.Opening song: schwarzweiß～霧の向こうにつながる世界～ (schwarzweiß ~Kiri no Mukou ni Tsunagaru Sekai~ / schwarzweiß ~Worlds Connected Beyond the Mist~) by Haruka Shimotsuki+Revo
Insert song: Flowers In The Rain by Rekka Katakiri
Ending songs:Lorelei by Noriko Mitose (Normal Ending)
大切なことば (Taisetsuna Kotoba / Precious Words) by Yuuko Ishibashi (True Ending)
Atelier Iris 3: Grand Phantasm received mixed reviews, resulting in an aggregated score of 64.78% on GameRankings based on 39 reviews and 63/100 on Metacritic based on 34 reviews.