Here's the list of all the creatures I've found, type these in the search bar, this is just to make stuff easier.

Watcher
Virus
Virus rage
Virtuey
soul
Nothing
Face
Circuit
body with soul
Blessed
BLACKOUT
The End (don't spawn unless you want your game to crash)
The Corpse of Exethronos, The Celestial Annihilator
DEATH
Chaos
siluet
Column
<COLOR=RED>C<COLOR=WHITE>H<COLOR=RED>A<COLOR=WHITE>O<COLOR=RED>S
(the name is chaos, but it's color codes, so you gotta type it in like that)

none of this includes the stuff you find on the main page, only the hidden stuff.

To find them you gotta type in the search bar, simple as that.