Jumong, Founder of Goguryeo

Also known as Dongmyeongseong 동명성, the ruler Jumong 주몽 is credited with founding the Goguryeo kingdom in 37 BCE, becoming the first Taewang 태왕, or "Highest King." There are a few variations of Jumong's beginnings in folklore and early mythological records, but one thing that is commonly emphasized is his supernatural and divine heritage.

According to myths and tradition, Jumong's parents were Hae Mosu, a sun deity, and Yuhwa, a daughter of a river deity named Haebek. Hae Mosu desired the daughters of Haebek and abducted Yuhwa. Yuhwa managed to escape before Hae Mosu's chariot ascended to the Heavens, but though she was a victim, her father condemned her for bringing shame. She was chased away to Ubalsu where the king of Buyeo, Geumwa, found her. Geumwa took her in as a concubine. However, through the magic of a sunray, Hae Mosu magically impregnated Yuhwa, causing her to give birth to an egg. Alarmed, Geumwa attempted to have animals destroy the egg, but the animals refused and instead protected the egg. Eventually, Geumwa ceased his attempts to be rid of the supernatural egg and returned it to Yuhwa, who cared for it until it hatched, bearing a boy. This child was Jumong.

From the beginning Jumong was a child of superhuman qualities. Just a month after his birth, he could speak. He was also a remarkable archer since a very early age. In one story of Jumong's childhood, Jumong used a bow and arrows to shoot down every fly that prevented him from sleeping.

The eldest prince of Buyeo was jealous of Jumong and thus consipred with King Geumwa to keep him at a lowly station by confining him to the role of stable boy. Knowing of the princes and the king's plot, he decided to establish his own kingdom. While working as a stable boy, Jumong with the help of his mother Yuhwa discovered which horse had extraordinary qualities. With this knowledge, Jumong made a plan to escape Buyeo. He put stuck a needle in the horse's mouth so that it would not eat. While the other horses grew strong, the special horse grew weak. King Geumwa took the healthy horses and left only the starving horse to Jumong. Jumong's plan worked and he pulled out the needle in the horse's tongue and went about restoring its health. Once the horse became healthy, Jumong, following his mother's urgings, fled Buyeo to establish the Goguryeo kingdom.

Sources:

http://www.prkorea.com/engnews/index.cgi?action=detail&number=435&thread=10r01

http://www.pantheon.org/articles/c/chumong.html