You are a summoner with the special ability to call upon legendary Heroes from different Fire Emblem worlds. In order to save the Kingdom of Askr from destruction, join the Order of Heroes and face a never-ending challenge."
Fire Emblem Heroes — also referred to as FE Heroes — is a Free-to-Play Gacha Game in the Fire Emblem series that was released on iOS and Android platforms on February 2, 2017. It is a crossover that features characters from across the series as summoned heroes, along with an Original Generation of new characters.
Set in the Nine Realms of the world Zenith, you, a Summoner, are called to assist the Order of Heroes, an organization consisting of Alfonse and Sharena, the prince and princess of the Kingdom of Askr, and Anna, general of the Order of Heroes, in defending the realm of Midgard from any and all opposing realms and characters that seek the destruction of Askr.
In Book I, the main enemy was Embla, Askr's rival nation within Midgard, as Princess Veronica leads the charge. In Book II, the sadistic king Surtr from Múspell invades Askr, as Fjorm from Nifl seeks help from the Order of Heroes. In Book III, the undead forces of Hel and their queen seek to swelter their numbers, as Hel's daughter, Eir, is captured by the Order of Heroes. In Book IV, the Order of Heroes end up in Ljósálfheimr, where they befriend the fairy Peony, all while nightmares from Dökkálfheimr and their queen, Freyja, threaten the Order. In Book V, the Order of Heroes are unexpectedly attacked by the forces of Niðavellir and their king, Fáfnir. There, after her defeat, Reginn joins the Order of Heroes against his adoptive brother, with the added help of the princesses of Jötunheimr. In Book VI, the conflict between Askr and Emlba reignites when Ash, the retainer to the God Askr, and Elm, retainer to the Goddess Embla, enter the picture. Between every book, Loki and Thórr lurk in the shadows, knowing more than anyone else combined in the Nine Realms...
Over the course of each Book, new content gets added to the game. Book II introduced the concept of "Legendary Heroes", special and strong heroes with unique skills that give elemental effects to those with the same elemental blessing. Book II also introduced the Weapon Refinery system, allowing units to be buffed by upgrading the effects of their weapon, or giving them a new weapon entirely and the Aether Raid mode, a new form of player-vs-player in the same vain as the "My Castle" from Fire Emblem Fates. Book III first introduced Beast units, units able to transform into any animal besides dragons, such as the Laguz from the Tellius duology. As well as this, Book III introduced the addition of four new seasons, and a new Hero Type called "Mythic Heroes". Book III also saw changes made to the merging system with the introduction of Dragonflowers as a way to boost the raw stats of units, and Duo Heroes, special heroes that consist of a pair (or more) of characters fighting together with a unique ability to them. Book IV introduced the Feh Pass, a subscription service feature that gave access to things such as special costumes for certain units on a monthly basis, special monthly quests, and other features. Book IV also marks the addition of the Trait Fruit, a way to change a Hero's Asset and Flaw at will. Book V brought a new type of Mythic Hero blessing mechanic that allows a sixth ally to fight in Aether Raids, and some more changes to the summoning system. Book VI brings in Summoner Duels, a new vs Mode that allows players to pit five of their units against each other. Book VI also introduced Rearmed Heroes, another new type of Hero that can pass on their skills and even their powerful weapon to another unit, but still remain in your barracks afterwards.
Heroes simplifies the traditional Fire Emblem gameplay to be more conducive for the mobile format. Maps have been reduced to a 6x8 grid, teams are only made up of 4 characters, there are only 4 types of units in lieu of a formal Character Class system, and there are less stats to keep track of. There are also no elements of randomness in combat, as all attacks are guaranteed to hit and Specials will trigger based on a counter.
Heroes was given an online spinoff comic, Fire Emblem Heroes: A Day in the Life, as a result of its success.
Due to the nature of the game being a crossover from all of the games in the series, spoilers for those games will be unmarked, up to and including Three Houses.