Grandpa Is Fighting Zeus in the Underworld. Should I Burn a Nuclear Bomb?

Lu Xuan is eighteen years old. Ten years ago, his grandfather passed away. Though death and parting are ordinary parts of life, honestly, Lu Xuan wasn't sad at all. For the past ten years, he had dreamed of his grandfather once every month. And whenever his grandfather appeared in his dreams, he would ask Lu Xuan to burn things for him. Lu Xuan was a devoted grandson, and whenever his grandfather asked for something, he would find a way to do it. It was just that his grandfather's appearance in these dreams seemed a little off... At first, his grandfather wore a burial shroud. "You little brat, the Underworld's in chaos. Those birdmen from the West keep invading. Burn me some weapons and gold ingots, and I'll recruit an army and wipe the floor with that damn Lucifer." Later, his grandfather changed into a smart military uniform. "You little brat! Burn me something with more kick. Those guns and cannons aren't enough to beat that bird-brained Zeus or whatever her name is, Athena." Then, at last, his grandfather came up to the world of the living himself... "Stop sleeping, you little brat! The barrier around the human world has shattered, and the situation is critical. Hurry up and cultivate these techniques! Then the two of us can team up and crush those Western bird gods." Lu Xuan jolted awake. Several cultivation manuals had appeared in front of him. Not long afterward, the sky split apart, mountains collapsed, and oceans overturned, as powerful demons and evil spirits returned to the world. Yet soon after each one appeared, a figure would beat it half to death, then ask the same question. "Tell me, how do I get to the Underworld?"