So guys you know How Bloodbending is a sub element of Waterbending and earth is the opposite of water in the series? Well They could make a new sub-bending similiar to Bloodbending But it will be a sub-bending of earthbending called Bonebending. And Bolin can be the the first one to create that sub-bending for earth since He always wanted to accomplish the feat Metalbending ever since he heard about toph being the first bender accomplishing that feat but the realize he's not able to metalbend but then somehow He uses bonebending to defeat Ghazan. Bonebending means to control the minerals in a person body. Like how Bloodbending is to control the liquids in someone body. Tell me what you think.