Smaug

Smaug(also known as Smaug the Magnificent) is a massive dragon that exists in J.R.R Tolkien's Middleearth Universe. Smaug is strong, versitile, and quick and his scales can break anything like arrows.

Smaug is also a fire drake from the 3rd Age and was the last "great" dragon left in the Middleearth

It's characteristics
Smaug is different from the other bad guys in BOTU. He has the attitude of an actual king, His stomach has gold inside of it as seen inundefinedThe Hobbit:The Desolation of Smaug. As Smaug said in the movie, he cant be killed normally but he has a weak spot, the Black Mark

Its significance in BOTU
Smaug is in his own side, and he heard about the Enclave and hates them but does not like the Rebellion eather. Later on the story, he attacks both an Enclave airship and the Rebellion HQ.