avatar the master of air

This is only a fanfic and I don't own avatar or any of the characters from their I only own my character.
He was the freind of the avatar before he vanished and his kind was annihilated.
' how could they those damn fire nation bastards how could they kill them all and why didn't aang who is the avatar come here to protect us why! Why' I could suddenly feel the air particles and could feel the world around me even after losing my eyesight to those damn fire benders I could even bend these vibrations. ' wait there is something over there what is it it feels massive.
" who are you mortal are you an air bender "
" yes"I reply
" oh so it seems you are strong well then let us make a contract I the king of air will give you even more mastery to air bending and will give you immortality if you end this cycle with the avatar and help the next ones in their goal"
" I accept your deal"
Will Have some characters that are not there and have some stuff that is purely my creation so it won't exist in the avatar world