Hoping someone can help me with this: If someone is hit with a Soul Bind spell (or other effect that removes and traps their soul in an object), can you use Discern Location to find the soul that is separated from its body? I assume that if the players saw the event happen, they would have seen the gem used and could try Discern Location on it, but in this scenario, it happened "off screen," so the PCs cannot search for it, so are trying to locate the soul itself. If Discern Location wouldn't do the trick, what might? Thanks for any guidance you may have.
Depends on how you use Discern Location, i.e. to locate the soul or to locate the gem holding the soul?
A discern location spell is among the most powerful means of locating creatures or objects. Nothing short of a mind blank spell or the direct intervention of a deity keeps you from learning the exact location of a single individual or object. Discern location circumvents normal means of protection from scrying or location. The spell reveals the name of the creature or object’s location (place, name, business name, building name, or the like), community, county (or similar political division), country, continent, and the plane of existence where the target lies.
To find a creature with the spell, you must have seen the creature or have some item that once belonged to it. To find an object, you must have touched it at least once./
Like you said, it happened "off screen", so you can't find the gem since you haven't touched it. The soul itself however, can be found if you've met the person before being binded to a gem, or have some of its belongings.
If you're high enough level to use Discern Location you're also high enough level to be aware that trap the soul exist and then can cast commune and ask a higher power if the soul of X has been trapped into a gem.
In fact, you can really develop a series of yes no questions to narrow down where it is and who has it.
Is the soul available for resurrection?
Is the soul trapped in a gem?
Is the gem on the material plane?
Is the gem in Avistan?
Does BBEG have the gem?