Some more concept stuff, also some input from people would be awesome.
Yoten: A rebellious Air Nomad who left his tribe in search enlightenment and adventure, he's mischievous and clever and yearns for excitement in his dull life as a monk. He meets with the others because he senses a spiritual disturbance and seeks to write the wrong and bring peace to the region terrorized by Lu Gao.
Lu Gao The Merciless: An ancient earthbending warlord from the time of Avatar Wan, a devout worshiper of Vaatu, he was granted the secret ability of energybending for his worship, he along with 3 other bending warlords had their spirits trapped into ancient masked by the second avatar, 500 years later an unfortunate waterbender is drawn into his tomb by his spirit and puts on his mask thus becoming Lu Gao.
Kouri: A calm and collected young man who was friends with the waterbender turned spirit warlord, he seeks to restore his friend back to his former self and stop Gao from conquering water tribe colonies located in the southern tip of the earth kingdom.