Leviathan

Different cultures have their own name for the Leviathan. The giants gave it the name Jörmungandr, the folk of Minowan call Bakunawa, and in draconic it is called Basagin. The seas of Sylvane are full of monstrous creatures, including sea serpents. But the Leviathan is no ordinary sea serpent: it is enormous, long enough to nearly encircle the globe. Its origin is unknown, but scholars of religion believe it is a titan stranded in our world, and distant relative to the dragons.
In the old days, the Leviathan roared up from the seas, tearing down coastal cities and wreaking havoc on those who dared to travel by boat. Legend has it the serpent did the bidding of Taniyn, and when she was imprisoned in the moon, the Leviathan took flight to devour the moon and free her.  The other gods tied Chauntea's millstone around his tail, sending him tumbling back into the sea. These same legends say that it swims round and round Sylvane, attempting to catch its tail, and when it does it will remove the millstone and take flight to eat the moon.
Rarely, sailors traveling through stormy waters will reach the shore claiming to have seen its scaly hide beneath the rolling waves.