User blog comment:Jack Pistol/Immortal Dovahkiin?/@comment-30303790-20121002201052/@comment-2040576-20121002202201

I think that there is definitely enough evidence to show that dragons' souls are not entirely immortal and are susceptible to death at the hands of the Dragonborn (the only known way to properly kill a dragon at the moment).

I almost overlooked the fact that an external party must resurrect the dragon. It is something that seems obvious, but is actually rather crucial. Perhaps only a select few have this power, such as Alduin? I wonder if the Dragonborn does?