The Amphithere

The Amphithere is a mysterious deep see dragon, rarely seen by surface dwellers, and the stuffs of legend amongst the seafaring races. The beast has a long, snake like body with a pair of wings nearly as wide as the creature is long. The tip of its tail has numerous boney spikes which it uses as its primary method of attack, whipping its tail at the target, potentially stunning or impaling its prey. The beast possesses a breath weapon, like most dragons, though it is uncommon for it to use it unless it is in serious danger. The wings serve primarily as paddles to propel the creature through the water. Their capability of flight is limited and rarely will the creature breach the surface except to mate or escape danger. 
seamount
It is exceedingly rare for any intelligent creature to slay an amphithere, as they are rare and live in difficult to reach biomes, however the scales themselves are incredibly valuable, as the creatures innate physical resistance can be harnessed from these scales to make exceptional plate armor or shields.