I was on my way to do a Companion initiation trial with my escort when a dragon swooped down and started a fight. We hit him a couple of times, then he backed off. He landed next to a giant and smacked it with his tail, which pissed it off and made it attack him back. The dragon took a light beating and then flew off again, this time landing in between two mammoths that he decided to roast with fire breath. Both mammoths got pretty mad about that and stomped the dragon to death.
Then I got the soul.