Red star: Gates to hell

In a far away land there exists a clan long famed for their strength. That clan is called the heirs of fire who inherited the very first flame. A certain young man who is named Hi meets Sozin a monk on his path to become a master. That is the beginning of long journey across the lands where they encounter a multitude of strong foes ranging from all manner of Monsters to Demon and Humans. Someone is plotting to open the gates of hell to unleash a demon plague on humanity. Will Hi and his party be able to stop this evil plan?