[quote=Aragorn]
Could a Soul Existence user discover the spirits? Or would that only be possible for a Spirit user?

Also, you are gonna need to tell us about that weapon of the soul...
[/quote]

[@Aragorn]
Soul users can see shimmers and undefined features if the spirits have died recently, usually within a month. After that, the Soul would have deteriorated too much for them to be seen by anyone other than Spirit users.

Weapon of the Soul got you interested? Wait for the Math teacher. They will be a Soul user for various reasons. Their extra info will explain how it works (and again, the compendium will made... Eventually. I'm procrastinating, I know.)