From Human to Indescribable

(Cthulhu + non-human protagonist + no Virgin + non-invincible + slow pace + no heroine) This is the third weekend without sun. At first, Meng Chi just felt that the rain had been falling for too long. Until. The smell of rotting fish filled the residential building. The sea level stirred up waves, and huge cities rose from them. The blood-red full moon suddenly opened countless eyes. An indescribable existence from the distant universe. Only then did Meng Chi realize that the rain-shrouded city in front of him was just the shallowest layer of the truth. And he himself was becoming... No longer like a human being. (Note: The protagonist did not mutate from the beginning)