http://fireemblem.wikia.com/wiki/Sully
Sully is a member of Chrom's Shepherds, and was born into a long line of Ylissean knights. She is the mother of Kjelle, and can potentially be the mother of Lucina and Morgan.

Sully is first introduced in Chapter 1, where she finds Chrom after the Outrealm Gate opens, sending in Risen soldiers. She is unknowingly tailed by the archer Virion, who almost instantaneously attempts to flirt with her. Sully, repulsed by his advances, brushes him off with a piercing word and a well-landed kick, before rushing to serve as a reinforcement to bolster Chrom's attempt to defeat the Risen in the surrounding vicinity. She then accompanies Chrom during the ensuing Ylisse-Plegia war, the Conquest of Valm, and purging the continent of Grima's influence.