A motherly and religious woman, Mercedes can't ignore people in need, being always prone to help her friends if there's a problem. She tends to let people tell her what to do, rationalizing this to be the will of the Goddess. She is good friends with Annette.
In-game, Mercedes is one of the best healers available to the player, being one of only two characters with access to the Fortify spell (the other being Flayn). She also does reasonably well with offensive magic, but she has terrible physical stats.
Mercedes's half-brother is Jeritza von Hrym, who was once known as Emile von Bartels. The two were separated when Emile's step-father, Baron Bartels, attempted to dispose of his wife, Mercedes and Jeritza's mother, and force his step-daughter to bear him a child with the power of a Crest. However, his plan was stopped by Jeritza, who killed his father before running away.
