This is Proteus' default form, aka Autozakretian form :3 that's what he is.

I wanted to do the whole white belly underside thing but it looked pretty strange with the way the body is segmented (like how I draw my insects)

The design is reminiscent of the first Autozakretian I drew years ago, but also a little bit(!) more feminine. Fall for the trap!

In Autozakretian form, his skin is very smooth and somewhat metallic feeling, his senses and abilities are reverted to normal (which is heightened when comparing to being shapeshifted)

Old GIF demonstrating the shapeshifting to Shark form