Emperor Ko (シコウ, Shikou) was an character mentioned in Golden Sun: Dark Dawn, and was the founder and the first emperor of the country of Sana. Though he died prior to the start of the game, and thus is never seen, his actions do have a minor effect on certain plot events.
During the thirty year period between the Golden Sun event and the start of Dark Dawn, Ko was known for being aggressively expansionist. To this end, he approved military actions to take over the eastern regions of Angara, such as the beastman region of Morgal. The country also had other colonies, most of which go unnamed.
Emperor Ko was noted to possess a desire for eternal life, similarly to Babi, the ruler of Tolbi. In fact, certain records make mention of Babi's knowledge, but notes that these secrets died with him. In addition, it has been theorized that Ko's reasoning for invading and controlling Morgal lay in a legend that Mountain Roc blood granted eternal life.
However, Ko would eventually die, leading to the breakout of a massive civil war in Sana. Ko's intended successor was King Wo, who shared many of Ko's expansionist views. However, Wo had left Sana proper to found the colony of Kaocho. The end result of the civil war was that Wo's rival, Unan managed to claim Ko's throne. Unan, a scholar, brought much needed peace to the region, but most of Ko's conquests were lost as a result.
King Wo would return to Kaocho, which he established as his own kingdom. Wo would continue Ko's legacy via his military aggressiveness and a mentioned desire for eternal life.