In the Extremely Cold Apocalypse, I Use the Lifespan of Monsters and Beasts to Build a City

Consume life span to speed up the construction of defense towers. Shen Wangjin's mortal body only has a lifespan of less than a hundred years. A piece of imperial edict of defense threw him into a desperate place full of beasts. He was apparently guarding the border, but in fact he was feeding the beasts and abandoning his son. Fortunately, you can get the opponent's remaining lifespan by killing the beast. City walls, sentry pavilions, garrison towers, thermal pavilions... Buildings were pulled up from the ground one after another. Until—— When the "Ultimate Disaster" comes, countless cold beasts tens of meters high spew cold mist and endanger the world. A city spanning thousands of miles across the continent rose out of thin air! … Occasionally, Shen Wangjin would be in a daze and meditate: I obviously spent my life to build the city, so why am I killing more and more of my lifespan as I use it more and more?