In a Weird World, I'm Martin the Shape-Shifter

No one knows when strange beings first appeared in this world. To fight them, humanity developed Awakened Ones, whose bodies and souls are extraordinarily powerful. Once they reach a certain level of cultivation, they can move mountains, fill in seas, and extend their lives. They can even slay powerful strange beings. But these creatures grow quickly and come in great numbers, leaving humanity struggling to survive in the cracks. It was only when a crazy, cunning wildcard appeared that humanity finally rose again.