In Bloody Kithicor: Part of the raid expedition "Bloody Kithicor".
On Thuliasaur Island: Galeth Veredeth (click for map image) is a roamer northwest of the tower north of the dock area. He also appears in the mission "Fit For the New World" (see this quest entry for details).
In Arx Mentis: Galeth Veredeth appears in the missions "All Rivers Lead to the Sea" (see this quest entry for details), "The Cost of Balance" (see this quest entry for details), and "Confronting Calix" (see this quest entry for details). He also appears throughout the raid zone (see this quest entry for the raid expedition overview).