Board Thread:General Discussion/@comment-24402683-20131207220158/@comment-202.156.8.11-20131209140753

I think they just mill about in the Dragonborn's body till the dragonborn dies. Then they get released or absorbed into another dragonborn, just like how Miraak can give you multiple souls (if they were destroyed, you will get only 1 soul from Miraak)