Galen Agaris (known as "King Horn", is the Japanese version) is an important figure of the army fighting against Emperor Griffon in Dark Cloud 2, he is encountered in Chapter 5: The Conflict of the Past and Future after completing the Georama requirements to make the Operations Room, where he meets Maximilian and learns of Monica's "capture". Galen gives Max the Fire Horn to help him reach the mouth of Mount Gundor and rescue Monica from Gaspard.
Galen is one of the highest ranking army members, the other being Elena, Max's mother. It is possible that the reason he is so high ranked is because of his friendship with King Raybrandt, Monica's father.
Galen is one of the supervisors of Paznos, the army's ultimate weapon, and can be found there after Chapter 5.