Question: who are the six flying dragons?
Answer: Yoo Ah-in as Yi Bang-won (later King Taejong) ... 
Kim Myung-min as Sambong Jeong Do-jeon.
Shin Se-kyung as Boon-yi. ... 
Byun Yo-han as Ddang-sae, later Yi Bang-ji, the best swordsman of Samhan Korea. ... 
Yoon Kyun-sang as Moo-hyul, the best swordsman of Joseon. ... 
Chun Ho-jin as Yi Seong-gye, (later King Taejo)