Klauth

Klauth, known as Old Snarl, is supposedly one of the oldest dragons alive who has not been turned into a dracolich. He is thoroughly evil, especially to his own kind, though he does have a few redeeming factors such as granting boons to creatures he considers no threat, crushing the odd orc horde on a whim and the fact that he has avoided the advances of the Cult of the Dragon. For such an active dragon of his age, he has lived much longer than his race's life expectancy would normally allow without the aid of the cult's methods. This is because he has developed a magical process in which he can use the eggs of red dragons to increase his own size, health and vigor.

Klauth makes his lair in the northern Sword Coast, in a narrow winding valley dubbed Klauthen Vale in the mountains west of Mirabar. From here Old Snarl uses his powerful scrying spells and abilities to learn as much as possible about the other inhabitants of the Sword Coast, this means the old wyrm is rarely caught off guard by intruders.

Video Game Apperances
Klauth makes an appearance in the game Neverwinter Nights, where players may either strike a deal with the ancient wyrm, or attack the wyrm. It should be noted that the Klauth in the game can be easily defeated if you perform the right actions, and of course this event is not canon to the Forgotten Realms world.