Kingmaker/Battles of Ardania
Goblin Archers are a type of Goblin in Kingmaker/Battles of Ardania, they spawn from the Goblin Archers Guild. They aren't the best archers.
Monster Kingdom
Goblin Archers were, like Goblin Spearmen and Shaman, originaly monsters in
Kingmaker, but become heroes after you free them from the control of the Rangers Guild int the quest New Subjects of the King in Monster Kingdom. They replace the Rangers from the original, they are hired from the Goblin Archers Guild.