Somewhere below mundane reality are metaphysical forces with an unwavering hatred of all existence, things that want nothing more than to cause harm. But these forces can't act alone. They need to be invited. They need permission. It takes discipline to allow them into your life without destroying yourself in the process, but if you can manage that, you can count yourself a Maledictor, a speaker of curses.
The effects of Malediction are many and varied, but they all involve something bad happening to someone else. Some curses have mundane effects, such as boils, or a run of bad luck at the card table. Others have effects that are more obviously supernatural, such as growing a pair of donkey ears, or being able to speak only the truth. Some are brief, others last generations, or as long as some condition holds. A solid, lasting family curse is a life's work for an accomplished Maledictor. Curses that affect an entire town or nation are the stuff of legends.
Curses are cast by getting into a specific state of mind and then saying words. Usually the words are a simple description of the curse's effects, like "May you reek with a corpse-like stench that no water can wash away", but there's considerable room for personal stylistic variation. One curse any Maledictor can do is the Withering Curse, which simply reduces the victim's life force, and can be invoked by shouting "Die!"
I'm reluctant to commit to a specific "spell list", because it seems like part of the fun here is improvising particularly appropriate or devastating curses, but we'll need some general rules for determining a curse's cost based on its severity and duration.
COSTS
Malediction is one of the most dangerous arts. Like a dam holding back unspeakable horror, the Maledictor's power is not a matter of how much they can unleash, but of what they can get away with. After all, one of the basic rules of wild magic is that the harm you do to others will return to you. (This is why the most powerful curses are those uttered with one's dying breath. It's the one time you're completely unconcerned about consequences.) But magic is all about bending the reality's rules, and Maledictors have certain mental gimmicks to avoid paying the karmic price of their actions.
The Maledictor's most elementary tool is RESENTMENT. The basic idea here is that the Maledictor can avoid consequences if he, or something he's greatly attached to, has already suffered enough harm at the hands of the other party, as this makes the Maledictor something like an agent of the cosmic justice that he's trying to avoid. Cursing someone discharges a certain amount of resentment determined by the severity of the curse (and possibly other factors). Resentment can be thought of as Maledictor mana, except that unlike normal mana, it's already directed towards a specific target.
Resentment towards a target can be increased by meditation exercises called BROODING and SEETHING, and even redirected to a different target with sufficient rationalization, but these things take time. The quickest way to gain resentment toward someone is to let them abuse you.
Maledictors tend to be celibate. This is not an absolute rule, but it helps with the brooding.
RESTRICTIONS
Curses must be delivered personally, in the form of spoken words delivered audibly. This means that you can't cast curses while gagged, or put a curse on someone who's out of earshot. It doesn't mean that the target has to hear or understand the words -- animals can be cursed, as can deaf people.
(Curses of the "Mummy's Tomb" sort are either a lost art or part of a different school entirely.)
TRADITIONS
There have been Maledictors throughout history, and they figure into myth and legend, but they don't have much in the way of organization, and dedicated Maledictors are relatively rare. It's more often practiced as a sideline: some magic schools teach a little Malediction as part of a general magical education, and your typical rural witch will practice it for personal defense.
There are two ways to practice Malediction as a vocation: offensively and defensively. An offensive Maledictor lives in poverty, hiding their powers, seeking out degradation and scorn, provoking bullies, and brooding a lot. This gives them lots and lots of resentment that they can use in curses. Offensive maledictors are sometimes "hired guns", but usually just pursue their own agenda, in which case they support themselves through either mundane labor or extortion.
Defensive Maledictors, on the other hand, don't go out of their way to make trouble. Since they don't cast curses very often, the few that they do cast involve lots of pent-up resentment, and tend to be powerful and, most of all, noticable. Their entire purpose is to make you think twice about attacking them or whatever is in their protection, so every curse has to be a spectacular public display with lasting effects, and even when not actively cursing, they adopt ominous affectations. A defensive maledictor is often the least popular member of a king's court.
Access: Learning Malediction is dangerous and not all that appealing to most people (especially after the first couple of mishaps), and illegal in many places (although laws against practicing Malediction tend to go unenforced for practical reasons). It takes a certain knack to get into the right mindset, but it's something most people could pick up if they wanted to. Beyond that, it takes years of practice to learn where your limits are and how to expand them. Most Maledictors seek some guidance in the early stages, but it's ultimately something you have to teach yourself. The greatest Maledictors tend to be entirely self-taught.
Social Status: Generally reviled and feared. Even if you're not driven mad by your own curses, there's a general assumption that anyone who chooses Malediction as a career can't be quite right in the head. However, it's pretty easy for an individual Maledictor to become a folk hero to the local population by afflicting those who are seen as deserving it.
SCHOOL
The Covenant of the Hood is a secret society originally founded to enable mutual cooperation between Maledictors in their individual quests for vengeance, but now it exists mainly just to perpetuate its own existence. They recruit students who show aptitude for Malediction in magic school and offer to show them greater powers in exchange for their loyalty (an empty promise because, as pointed out, Malediction is something you teach yourself, but once you're in, it's hard to leave). Their motto is "An injury to one of us is an injury to each of us". They have infiltrated various governments and institutions, and could probably rule the world if it weren't for the fact that the members all hate each other.
Scattered: Every major city has a lodge hidden somewhere.
Incompetent: They're largely mad, there's a lot of
infighting, and the veil of secrecy prevents them from cooperating
effectively at more than a local level.