Galactus is starving and must consume a planet soon to survive. Using what little energy he has left, he comes to a very primitive planet compared to past planets he's conusumed. He figured his heralds should be able to prepare the planet alone with him nearly incapacitated. He then sends his heralds down to the planet to prepare his feast. If they don't succeed it will be the end of Glactus. So it's The World of Avatar not long after Aang beat the Firelord VS. The Avengers:EMH versions of Air-WalkerFirelordStardustTerrax For Planet Avatar to win, the 4 nations have to work together to destroy all 4 machines each herald will place. Each herald will place their device somewhere in their respective element kingdoms. Once a herald's device has been destroyed, Galactus can't rebuild it. The heralds win if they succfully feed the planet to Glactus of course. Notes: Stardust's device will be at the Northern Water tribeAir-Walker will be in the Southern Earth Kingdom since the Air Temples will are abandoned at this point in timeTerrax will be making his machine in the center of Ba Sing Se and will announce Galactus's arrival and what not like he did in the Avengers:EMH cartoon (if I remember correctly)