A leviathan is a dragon type sea monster that looks like a serpent, but can have wings.
Some breathe fire, some have control over the elements such as oceans and wind
They all have sharp teeth, and mostly all of them can use the sea to their advantage;
they can control it.
They look very organic and monster-like.
The Loch Ness monster is sort of related to a leviathan.
look at this final fantasy evolution of Leviathan
http://www.ffcompendium.com/h/espmon/leviathan.shtml_________________
