I Keep a Low Profile in the Black Sea and Raise My Way to Immortality

Raise crabs, and gain one point of pincer strength: your hands can crush metal and stone. Raise green-scaled fish, and gain one scale: your skin can transform into fish scales. Raise turtles, and gain one year of life: you can live forever... When humans come, I’m a formation master. When demon beasts come, I’m a fish demon. When magical beasts come, I’m Cthulhu.