Hydreigon

Sazando is the final evolution form of Monozu. It now has heads on its arms, ending the Hydra-like evolution stage.

Pokemon Black Japanese Pokedex Entry
A brutal Pokemon that flies continuously through the sky on its six wings, marking everything that moves as an enemy and attacking.

Pokemon White Japanese Pokedex Entry
''The heads on its arms lack brains. It destroys and devours everything with its three heads. ''