“Hmm... There must be a reason that you attack this castle... But what...?”
Raeth (also sometimes known as Reis) is the boss of Chapter 15: The Dragon Girl in Fire Emblem: Binding Blade. According to the in-game dialogue, he is a General in Bern's Army. Raeth is charged with defending a small fort on the Etrurian border, where Fae is imprisoned.
“Gah...! That girl...she isn't human, is she! Why...do you seek her...! To use her power...? ...!”
—Raeth's death quote in Binding Blade.