Thaelin

Thaelin was one of the largest known dragon turtles in the history of Toril.

Description
Thaelin was known to be roughly the size of an island.

History
Thaelin originally dwelled in water-filled caverns beneath the slopes of the island Tharsult. When the dragon turtle's plundering of ships eventually threatened the shipping and commerce of the island, they employed a large number of wizards who managed to slay the beast.