Volvagia, also known as Barba, is a snake-like dragon that has been featured as a dungeon boss twice in The Legend of Zelda video game series.
The Adventure of Link
Barba is the guardian of Three-Eye Rock Palace, where Link places one of the six Magic Crystal shards in the palace's lectern in order to rouse Princess Zelda from her unnatural slumber. It breathes fireballs at Link. However, it can be beaten if Link uses the Jump Spell, or by using the upwards sword thrust, though this method is more risky, as it is easier to fall into the lava. It's better if Link stands still and facing it to prevent this while using this technique.
Ocarina of Time
A legendary, snake-like dragon in Goron lore, Subterranean Lava Dragon: Volvagia is the boss residing in the Fire Temple. Volvagia was an ancient dragon that lived in the depths of the fiery Death Mountain, long before Link was born. It was said that a legendary Goron destroyed Volvagia with the use of the Megaton Hammer. By the time of Ocarina of Time, Ganondorf had revived the fierce creature to secure the corrupted Fire Temple from intrusion and by feeding the native Gorons to Volvagia, to "make an example" to other people that might revolt against him. Incited by Darunia's son, Link set on to destroy Volvagia or else; if the dragon escaped from the temple, Hyrule would become a burning wasteland. In the game, Volvagia is referred to as "it" with a single instance in which its gender is specified as male. This is omitted in the 3DS remake.
Ocarina of Time (manga)
The 2008 manga of The Legend of Zelda: Ocarina of Time has an entirely different backstory for Volvagia. In it, Link buys Volvagia at a shop when he's a baby and Link a young boy, and the two have some bonding time before Link sends Volvagia on his way. Sometime during Link's seven year sleep in the Chamber of Sages, Ganondorf finds Volvagia and turns him into a monster through some kind of mind control, destroying Goron City and threatening to bury all of Hyrule in lava from Death Mountain. Link has to make the tragic choice to kill his old friend in order to save Hyrule. As Volvagia's severed head hits the ground, it cries and says Link's name one last time.