Valter (translated Walter in the Japanese version), also known as the Moonstone, is third strongest general in Grado's Imperial army, both in the past and the present.
Valter is a sadistic Wyvern Knight who wields his Lance with unsurpassed skill and strength. During his past career as a Grado general, Emperor Vigarde fired him for slaughtering innocents - but when the Emperor "changed" from the powers of the Dark Stone, Lyon ordered that Valter be re-hired. Valter was also present during the siege of Castle Renais, in which he and 4 Wyvern Rider sentries were patrolling the area, when he had spotted Eirika and Seth escaping from the castle. He then proceed to attack Seth, giving him a strong wound in his arm. Seth and Eirika then ran to the Renais-Frelia border area, where Valter said to his sentries to let them go, and in his words: "More time to savor the hunt...and the kill." In chapter 5x, he places his aide Tirado at command of Castle Renvall. Much later (seen only in Eirika's route), he duels with General Glen the Sunstone for opposing him and allowing Eirika and her party to let them pass to Caer Pelyn and Jehanna, and Valter ends up winning the duel, killing the other general, and had his and Glen's sentries to go after Eirika. Valter then brought Glen's mangled corpse back to Castle Grado to show his younger brother Cormag, then framing Eirika for his death, as well as giving morale for Cormag being the new Sunstone. Cormag then flew off to where Eirika and Princess L'Arachel of Rausten's forces were battling Aias and General Caellach the Tiger Eye's forces, accompanied by two Wyvern Rider sentries, but then joined Eirika after she persuades that she did not kill his brother. In Ephraim's route, Valter accused General Selena Florspar of the same treason General Duessel the Obsidan was accused of (failure to carry out orders), making Selena sail off to Grado as Valter places the Ranger Beran as commander of the forces at Bethroen, who fails and either dies or sails off in cowardice.
According to a support conversation between Cormag and Duessel, Valter used to be an only somewhat more decent and still sane man (though he wasn't "a gentle lamb before" as Duessel puts it) until, having had his own lance broken in battle, when Duessel wasn't looking he took a cursed lance owned by General Duessel, which made him into the man he is now. Cormag then points out a weapon is only as good or evil as the man who wields it. Valter also lusts after the beautiful and strongwilled Eirika, and one of his reasons to fight is his desire to capture her and make her his puppet bride; Riev points out, as he hears about it, that Valter is like an animal, not letting the human rules stop his darkest desires. He dies at the assault on Jehanna Hall. In Creature Campaign Valter is unlocked by beating the seventh floor of the Lagdou Ruins.