Something from the anime/manga series ‘Fist of the North Star’, meaning ‘you are already dead.’ And then the person it has been said to dies. If you hear this said, it is completely unacceptable to not say ‘Nani?!?!?’.
Ohmaygot Ambatubas was a Mongolian Emperor who reigned from -322 to 2012, Ambatubas was known by many and regarded as a hero. Whenever he rode into battle he would shout: "Am Batukam!!!" who was the brother of Ambatubas who sadly died in battle while fighting alongside their father Ambasing.
This is only used in the highest profiles of the highest edgy meme lords. it can be used to absolutely destroy an opponent in battle. Only the best can use it. It means “you are already dead” but will instantly kill your opponent in an anime battle.