Where to get : 
U can easliy get them from Quests and Bosses for
80/120/160/220/260/320/360 Lv.
Bosses like : Demodras;King Scorpainus;Spider Queen;Webster
What does the stone give us?
Simple it boost ur Bending techniques, example below.
Air stone first usage improve the Air Ball! Now it will always go in the double version. Earth stone first usage improved the Earth Crush! Your damage has been increased by 20%. Fire stone first usage improved the Fire Whip! Your hit area will now always be around. Water stone first usage improved Water Whip! Your hit area will now always be around.
