You can sell it off if you don't intend on playing any of the other characters.
Character slots are just different characters that you have. Their campaign progress is separate from each other. Money, equipment and the hirelings that you've acquired through bone resurrection is shared amongst all your characters.
This class advice post?
You need to equip the spell in your inventory as an item.
Ah, that explains it. Thanks! Are common skills passive or does that have to be equipped too?
Anybody have recommended spells for the Sorc?