As I'm sure you know, this month's RPG Blog Carnival is focused on curses, cursed items and campaign stories which feature cursed PCs. Historically curses are any expressed wish that adversity strike someone else, directed through foot tracks, the evil eye, book curses or any other method. Any sort of magical working that seeks to affect a person requires sympathy, you can read up on that here. A great example of sympathy and cursing at work is the story "La Vuelta de Culebra" translated to English in this book. Curses and cursed objects have a long history in RPGs, whether the bag of devouring or the King in Yellow, but beyond the bestow curse spell anything resembling the traditional form is quite rare. Especially considering how common curses are in real world cultures and stories.
Below is a Fate Core Magic skill that bears a close, traditional resemblance and will be used in the Wicked West. It is very similar to one of the magic subsystems in the Fate Toolkit with some stunts from the Secrets of Cats and other places.
Attack: There is no Attack with Magic.
Defense: There is no Defense with Magic
Create an Advantage: Magic can be used to create thematically "Cursed" or Blessed" Aspects on characters and objects you have a sympathetic link with.
Overcome an Obstacle: Magic can be used to remove the above mentioned Aspects with a ritual.
Astral Projection: Once in a trance, you may spend one Fate Point to send your consciousness and those in physical contact with you into the Astral Plane, leaving your husks behind until you return.
Pin Cushion: Once you have a bit their hair and an effigy, you can Attack someone with Magic. The doll is destroyed once you inflict a consequence but you can minimize the damage to stress. No limits on range.
Dowsing: You can undertake a mental challenge to seek someone out, difficulty will depend on how well you know them and if you have sympathetic link.
Warding: You can Create an Advantage on a zone that can also be used to Defend against outside attacks and efforts to enter the zone.
Claw, Mane, Wing and Tooth: After consuming a noxious concoction of animal humors you may Create an Advantage of shapeshifting, you can invoke this aspect for bonuses to do animal things.
Special: The Right Tools for the Job
When using the Magic skill to undertake any action there are two things to consider: sympathetic link and the equipment in use. You can still undertake a working without either, but your chances of success decrease accordingly. Without a link or the correct tools, the opposition receives a +1 to the roll for each missing element. Certain Stunts already specify the correct tools and the need for a link, depending on how well your character knows the target you may not need to forge a link with a particular individual.