Cultivation: I Refined the Calamity of Heaven into a Magic Weapon

On the day when the elders passed through the tribulation, Lu Chen and five apprentices were locked into the terminal furnace room. There are people outside who are ascending, but the people inside can't even open the door. When the thunder burned through the copper trough, Lu Chen discovered that the ancient furnace in his hand could refine the attenuated thunder into iron. His first weapon was a nail. He didn't use it to kill immortals, nor did he use it to become famous. He pushed the tip of the nail into the crack of the door catch to let all six people in the house get out alive. From then on, the scrap iron was put into the furnace, and the remaining thunder was turned into a weapon. But Lu Chen soon discovered that the people who were more difficult to deal with than the Heavenly Tribulation were those who locked the door.