Let us able to send a curse on criminals.

[Iva]

The more powerful and annoying debuffs - the weirdest ingredients. Maybe even not removable and inheritable, if it was used instead of sending nidbane. Witch credo maybe?
Make it so that only the victim or the victim's heir can send a nidbane or curse and only once per one crime, but this ability should not be limited in time by scent's disappearance - "Revenge is a dish best served cold."