Fafnir
Fafnir is a Draki variety of Dragon, and his origin is full of wild stories.
The most well known one, which is now known to be untrue since contact with the Aesir Gods post Ragnarok, is that he was originally a Svartalfar that lived in Midgard turned into a Draki through greed. This, he is not.
Fafnir is one of only two Draki which have had their existence verified; the other being Nidhog. Unlike Nidhog though, he lives on Midgard and wherever he goes destruction reigns. He is a husky brown in colour and despite his size, is very apt at disappearing without a trace after his destruction of wrought. Like the story of the Svartalfar he was meant wrongly said to be, he does have a hoard of gold, though its location is unknown. It had never been found.
He was eventually rumoured to have been killed by a Midgard warrior. The truth of this is unclear, and upon the Gods hearing the story of Fafnir's apparent demise; all they did was laugh.