The Light Brand (光の剣, Hikari no Ken, lit. Light Sword in the Japanese versions) is a magical Sword that concurrently appears in various titles throughout the Fire Emblem Series. As its name suggests, this sword is one that is imbued with Light Magic, that which its wielder can harness in order to perform ranged attacks by smiting his/her foes with the Lightning spell. To this end, the Light Brand may be regarded to be analogous to other magical blades manifesting in the series, such as that of the AnimaWind Sword and the DarkRunesword. Unlike these two swords, however, the Light Brand does not induce any additional side effects when employed, where it is neither effective against flying units nor capable of vampirically sapping the HP of selected enemy targets.
In the Jugdral Series of Fire Emblem, the Light Sword takes on a role that is of a fairly significant import; Initially functioning as a symbol of boon sisterhood between Ethlyn and Deirdre in Genealogy of the Holy War, the sword is, upon being inherited by Ethlyn's son, transformed into a cherished relic of her memory. This transformation is concretised in Thracia 776, where the fact that the sword is solely bound to Leif subtly connotes a protectiveness that he assumes over it, borne of it being the only keepsake by which he can remember his mother.
To determine the damage output that ensues when the blade is used as a ranged weapon in Rekka no Ken and The Sacred Stones, half of the wielder's Strength is first taken into consideration (round up if necessary), before adding it to the weapon's Might. Subtract the sub-total by the selected enemy target's Resistance, and the resultant value will essentially reflect the amount of damage that may possibly be inflicted.
In Binding Blade, the ranged attack's total might will always be 10, regardless of Strength and Resistance.
Another point of note is the fact that the Weapon Triangle mechanism is only taken into account during direct combat, while in the case of indirect combat, the Trinity of Magic system is considered instead.