Magical curses are rarely cast, as if cast on someone for fun or purely maliciously and the person cursed has not done something seriously wrong, it tends to ricochet back on the curser. Therefore the few who do get cursed are shunned by most people as genuinely guilty,and few will help them.
The words of a wedding vow contain a strong love spell which enchants both the people who says it, so they will allways be deeply in love with each other.
Little halflings are told that if they don't behave, a demon called Santa Claus from a hell of ice will kidnap them and force them to toil making toys.
The spirit of a creature trapped in amber cannot escape to it’s afterlife / next incarnation / whatever.
Such trapped spirits can be contacted by those who know the right rituals and magical power derived from them – typically the power to control one individual of that species.
Can by quite powerful if the creature is a colony insect (ant, bee, wasp, etc) – simply control the queen and you command the whole colony.