In light of the absolutly stunning image that  iflops did of Kacora's Leviathan form ( Seen HERE ) I thought it would be prudent to post what I've always pictured it looking like.

Remember, as a Shapeshifter, Kacora had no gender and no "true" form. They do regularly take the form of a Leviathan when very angry, very hungry, or when someone just plainly needs to die.

Note the thin (by comparison) ridges and spines on his Neck, back, and tail. These are defensive for the most part but have a sharp edge and can slice though the hull of a tanker or modern battle ship if stuck. The horns (similar in style to a rattle snakes tail, are made of many bone-like pieces that, on a normal creature, would indicate age. The tail is broad and flat at then end. Protected by heavy hairs and spines it uses this tail to no only help propel it thought water or into the air (like a crocodile) but also a a clubbing weapon. The fore-limbs are smaller and more articulate than the hind but both have webbing between the digits.