Fantasy: I Arrived in the Underworld at the Beginning

"I'm already dead? How is that possible?" Is this the underworld? Why is this happening? Instead of reincarnating, they let each other kill each other, just like raising gu, only the strongest one will be left. Is there someone controlling the underworld? Who has so much energy? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.