headcannons for them:

-they are natural herms
-the inside of them is made of a core goo kinda stuff,surronded by a hard shell.
-they dont have front arms,the one from their heads are the front arms,they can however create extra parts with they goo
-they can not by killed not damage by anything that is not fire
-they can re grow lost memebers by absorbing water,unless these where destroy by fire
-they hatch fromm egg,a soft texture eggs similar to jellyfishes
-they dont need food,they nuture by sun/moon ligth and water
-they can survive begin only the goo thing with out shell,but they need shell to have a form
-they can crossbreed
-they are more instintive than smart
-they have no gag reflex non inside organs
-they dont need to expel waste
-they sweat a lot
-they get slower in very slow temperatures
-they prefer the humid ambients
-they dont bleed
-the shell parts are flexible too,but can resist pressure and hits,they absorb damage,think like Luffy and his gomu-gomu
-the inside core goo can extend as far as three times their size,but if they try longer than that they can suffer from something very similar to anemia and faint.
-they obviously glow in the dark


last one of the base batch,from here i will take custom designs or crossbreed designs