Quote Originally Posted by Cleretic View Post
We actually may not have the power of possession, since that seems to be one of the various 'relatively special abilities' of the Echo that not everybody has. We've seen people with the echo die and not live on as a spirit (RIP Ysayle, who deserves much better), it's actually only the Sahagin Priest and Zenos that actually have the powers of possession. Also, if every Echo-user had the power to live on as a spirit, just by law of large numbers we'd have at least a couple more non-Ascian immortal spirits kicking around.

Of course, the question of if any Echo-user that hasn't already died has the power of possession is... kinda unanswerable, because I don't think anyone wants to run the only test that would work for that!
Minfilia also had the power of possession, but she liked to give her hosts choice and autonomy while giving them her power. If she were evil and self-serving she could have taken Ryne's body for herself.

As far as having other, non-Ascian spirits live on... see Tenzen. See Ramza. We do have them. They're just not common, as befits something special.