In the collegium you found the book: Darkness Biografy,you read it:
darkness is in everyone,an dark spirit is the evilness in the person it's in,if an dark spirit is unleashed,it can only be put back if it's owner.
there are only a few creature which can unleash an dark spirit:darklings,dark dragons,the oracle and the guardian of darkness.
If an dark spirit is destroyed,it's owner is unable to do any mental attack like swearing or using magic.
If the owner is destroyed,the dark spirit will live on as an darkling.
Any magic the owner posseses,the dark spirit is master of,if there's any ability that the owner doesn't know,the dark spirit can use it.
the owner only can counter the attack of an dark spirit while it will try to destroy it's owner.
behind where the book lied down,there's an dark dragon,and you run for your life