Viinturuth

Viinturuth is a named dragon found in the wilds of Skyrim. He speaks in native dragon tongue when in the presence of other dragons. He is aggressive and uses fire or ice, depending on your level.

He is often found in the company of Alduin, whom will not join in on the fight but rather fly off to let the Dragonborn and fight.

Bugs

 * After defeating Viinturuth it is possible that he'll attack you again and may be invisible. (PC, PS3 and 360)
 * When you encounter him Alduin may not finish resurrecting him. He will crawl out of the grave but remain a skeleton and he will not regain his flesh. He will not attack, but you can still kill and loot him and absorb his dragon soul. A column of the dragon soul energy stays above the mound as well. (Happened on Xbox 360)
 * Once, when I fast traveled to Dawnstar his corpse appeared in front of me. I'm not very far in the main quest, so I haven't defeated him - I'll get back on whether he was in the quest or not.
 * While playing through I noticed Alduin resurecting him, Viinturuth was stuck in the ground though, full resurected. He was just stuck, he couldn't attack and I killed him. Sort of, his health bar was fully drained but his name was still on the top of the screen and he was still moving a bit. Nothing could get him out of the hole, no amount of dragon shouts or staffs would work. So I went to the nearest mill, Angas mill. Waited three hours, and on my way back he was in a completely diffrent spot, on the road leading to him. I was able to loot him and get his dragon soul.