Lord Garmadon is a person filled with chaotic evil which was caused by The Great Devourer. When he was a boy he use to not be evil until a smaller version of The Great Devourer bit him and with its venom it fill him with nothing but pure evil. His only objective is to destroy Gumball Watterson and he plans on doing this by getting everybody to not like Gumball anymore even his family and Penny Fitzgerald. There was a time when he did request Gumball's help so he can destroy The Great Devourer, but after it was over it was business as usual. His brother is Sensei Wu and his son is the Green Ninja Lloyd Garmadon. He betrayed Megatronand said "If any one is going to take over the universe it will be me."
He's one of the characters that has the power to wield the Mega Weapon.