I'm at the End of the World, the System Tricked Me into Slaying the Dragon

"Three years later, the giant dragon will destroy the world, and a breath of dragon breath will shatter the planet! If you don't want to die, level up quickly!" Shen Yuan believed in the system's words and worked hard for several years to master the dragon-slaying skills, just waiting for a decisive battle with the giant dragon. The end of the world has come as expected, but there is no giant dragon covering the sky, only a group of slow-moving, howling little zombies. Shen Yuan looked at the dragon-slaying knife in his hand that could destroy stars, and was completely confused: "Dog system! Where is the dragon slaying we promised?"