Echidna rough sketch Picture

Alright, so I need to do concentration pieces (a 12-part series, basically), and I chose mythological creatures for my subject. I'm starting with Echidna, the Greek "mother of monsters." Don't expect the finished piece to be on this paper or look too much like this. This is just planning.
Cerbero
Sketch Phorcys
Echidna rough sketch
Sphinx
teumessian fox