The Starsphere Shards (星のカケラ Hoshi no kakera, lit. Star Fragments) are a collection of Stat boosters that exclusively appear in Book 2 of Fire Emblem: Mystery of the Emblem and its remake. Twelve fragments that are derived from the Starsphere, each shard corresponds to one of the twelve constellations. In order for the games to be completed, all twelve shards must be collected by the player, and it is entirely possible for them to be permanently missed due to careless oversights.
In Mystery of the Emblem, each shard provides percentage boosts to the growth rates of its holder.
In Shin Monshō no Nazo, the bonus provided by each shard is changed into directly boosting specific stats of its holder. These stat boosts have the potential to exceed limits that are imposed by caps.
After Gotoh created the Starlight spell in Shadow Dragon, the impact exerted tremendous strain on the Starsphere that it was not able to withstand, causing it to shatter into twelve different fragments.
The fragments then scattered across the continent of Archanea, and Sage Wendell was entrusted with the task to recover them in the events of Mystery of the Emblem. His efforts were stalled when he was captured by Archanea's forces and had his collection ransacked. Upon meeting Marth at the end of Chapter 6, he urges Marth to aid him in his quest, highlighting the calamity that could befall mankind should even one of the five arcane spheres of yore be lost. Marth eventually succeeds in finding all twelve across the chapters leading up to Chapter 14, which are then merged back into the Starsphere by Gotoh in the Ice Dragon Temple. In doing so, the newly-formed Starsphere combines the effects of all the greater Shards into one, providing boosts to all the stats of its holder.