I Just Want to Lie Down, but the System Wants Me to Conquer the King of Creatures

I died naturally in my previous life, and when I woke up, I went into another world. I wanted to survive my whole life by eating my old age, but I was told by the system that if I didn't kill or conquer the King of Creatures, I wouldn't be able to survive until 18? What else can I say? I must kill King Gui to straighten my way to peace! ! ! !