In Fire Emblem: Radiant Dawn, she is discharged from Begnion's Holy Guard, and becomes a member of the Crimean Royal Knights, along with her brother. Since joining the Crimean army, she has become a friend of Queen Elincia, but continues to be repulsed by Makalov's fondness for gambling and drinking.
One of Marcia's distinctive traits is the way she speaks. Often times, she will use words like "clambake" and "sponge-brain" as insults. In place of profanities, she will use words like "crackers", as in, "Oh, crackers!" or "Oh Chestnuts".