“A charm that increases resistance by 2.” —In-game description, Shin Monshō
The Talisman (魔除け Mayoke) is a Stat booster that recurs across the Fire Emblem Series. When used, the Talisman permanently raises its user's Resistance by a set number of points that varies from game to game.
In Genealogy of the Holy War, the Talisman is substituted by the Barrier Ring (バリアリング Baria ringu), and must be placed in the inventory of any unit in order for its Resistance-boosting property to take effect.
Enemy magic users are typically interspersed among mostly non-magical forces,and will only appear in large numbers near the endgame, at which point the player should hopefully have an answer to magic that does not involve clinging to a +2 resistance boost. As such, Talismans aren't as useful as they might appear. Nevertheless, the Talisman is a stat booster and as such is extremely useful.
Talismans should be consigned to the strongest physical frontline unit in a player's army, as such units will likely be able to benefit from the ability to take the occasional magical hit. Talismans can also be used to allow a unit to withstand additional assaults from long range tomes, such as Bolting. Units that can only wield swords are generally not the best choice for Talismans, as they will typically be incapable of counter-attacking against ranged spells and will rarely be a first choice for dealing with mages. Mages are also generally a poor choice for the Talisman, as high-end enemy mages typically have very high resistance to begin with.
As part of the Radiant Dawn storyline, Queen Elincia sews a Talisman onto Lady Lucia's collar in Chapter 2-2 as a lucky charm to keep her safe in the ensuing battles that she engages in on the behalf of her liege.