Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu is a Nintendo DS remake of the Japan-only Super Famicom game, Fire Emblem: Monshou no Nazo. More specifically, it is a remake of the second half of Monshou no Nazo, as the first half of the game was a truncated version of the first Fire Emblem. The story once again stars Prince Marth as he fights to protect his kingdom. However, the player does not play as Marth but instead as a custom character, a first for the series that was featured in all future entries in the franchise. Fire Emblem on the Gameboy Advance allowed players to create a custom character but the character, a tactician, held no actual significance in gameplay or the story.
The game's plot is a direct sequel to the events of Fire Emblem: Shadow Dragon. Players once again follow the protagonist Marth as a new darkness threatens to take hold of his homeland. Hardin, one of his allies from Shadow Dragon, becomes Emperor, but, for reasons unknown, is swayed toward the side of evil. Marth must reunite his allies from the previous game, gain the support of several new ones, gather the twelve Zodiac Pieces in order to reassemble the Fire Emblem, and determine the cause of Hardin's corruption.
The player follows Marth through the role of the Hero of Shadow, a new character introduced in the remake. The Hero of Shadow is a customizable character whose name, gender, appearance, and starting class are all chosen by the player.
The Fire Emblem series has always played on a grid much like other SRPGs, and long used the rock-paper-scissors method with its various weapon advantages. Being based on the second book in the original Mystery of the Emblem, it will most likely contain several of the gameplay aspects from that game. For example, there are twelve Zodiac Pieces that affect the growth of whatever character is carrying it. In addition, a new class, Dancer, will be added. Although not new to the series, its source material was the first game to have the Dancer class. As a trade-off, the Freelancer class will most likely not return, as the first Fire Emblem (along with its remake) are the only games in the series to feature that class; most others have used the Dancer class, or some variation of it.
This game also marks the first Fire Emblem where character deaths are not permanent. Although several games in the series (Ankoku Ryu to Hikari no Ken, Seisen no Keifu, etc.) feature methods of reviving characters, these instances are very limited and deaths are still treated as permanent. This entry, however, features two modes: a classic, which allows traditional permanent deaths, and casual, where death is not permanent. These are not difficulty levels, but supplements to them.
Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu was released in Japan on July 15, 2010, which was fairly late in the life of the DS. Perhaps because of Shin Monshou no Nazo's late release Nintendo never localized the game for other territories. However, a group named The Heroes of Shadow released an unofficial English translation patch for the game on November 21, 2012. The game's title was translated to Fire Emblem: Heroes of Light and Shadow.