A New Spellcasting System and a Spell

I haven't liked most spellcasting systems I've seen, so I've made my own.

You have a number of d6 equal to your proficiency bonus + your spellcasting ability modifier. If you're playing an OSR game, you have a number of d6 equal to your magic-user levels + your number of spell slots.

You don't actually have spell slots.

When you cast a spell, roll your pool of d6. You need at least a single 6 to succeed. Any dice showing a 1 are removed from the pool until you complete 8 hours of rest. If you have your success, voila, the spell is cast. If you fail to cast the spell, you roll on the spell mishandling table.

You can cast a number of spells this way equal to your total magic-user levels. Additional spells past that point require 1 additional success per casting. So if you're level 5, you can cast 5 spells for 1 success. The 6th spell will require 2, the 7th three, etc.

Spells are serious shit. They are esoteric, weird, powerful, hard to understand, and not always useful but always impactful. A wizard casting a spell is an impressive thing that creates legends and burns itself into the memory of all who see it. For this reason, you can only cast spells "safely" (read 1 success=cast) again after a week of meditation and rest, righting yourself with the world in the process.

This may seem restrictive if you're thinking of spells as one-off effects like Fireball or Magic Missile or Charm Person. But those aren't spells, those are the weak efforts of hack-wizards pretending to be the real deal. No, with this magic system, you don't bother with such trite shit. Instead, you cast real spells.

Below is an example.

Probably a Warlock, Witch, or Wizard spell.

MALEDICTION & MISFORTUNES BESTOWED UPON THY SOUL

Malediction & Misfortunes Bestowed Upon Thy Soul involves the ingredients of one ounce of innocent's blood, a lock of hair from your intended target, the heart string of a woman wronged by her lover, and an impossibly visceral hatred or sense of disgust at the target of the spell. Their location does not matter. Casting the spell can be done in a single instant, consuming all of the ingredients in a conflagration of nightmare-flame--black and slick as oil--or over an 8 hour period, in which case the spell's effects are greater than anticipated. The ritual for performing this spell requires an environment closed off from sunlight, filled with incense smoke that smells of corpses and strawberry, and candles arranged in three half-circles around the ingredients. 

Hatred and disgust are emotions easily weaponized by magic. The casting of this spell turns them into literal swords, invisible to the mortal eye, that fly through the dream-space of the mind and impale the muse and genius of a target. The target is allowed a save vs Magic (or Wisdom save for 5e). On a success, the swords are rebuked back on the caster, who must make the same save 24 hours later. This effect ping-pongs until someone is impaled or 8 days have passed. Once a target fails, their muse and genius are impaled. This, in turn, causes their fortune to bleed out. Within 24 hours of affliction, the effects of this are first seen.

Roll 1d6 on the table below for the initial effect. If you have spent 8 hours casting this spell, roll 1d6 times instead.

1. The target is struck by unseen paranoia. They cannot benefit from any sort of rest.
2. The target attracts the attention of thieves and con artists. Every 8 hours, someone will attempt to rob or trick the target.
3. The target's wounds, or any wounds they suffer from here on out, become infected. Their constitution lowers by 1 point each week. 0 constitution results in instant death.
4. Insects are attracted to the target. Their food is covered in cockroaches, maggots infest their wounds, and wasps beat the shit out of them every so often.
5. The 4 closest people to the target begin to lose their love for them. Within 1 week, they will no longer care for or associate with the target.
6. The God of War lusts for the target. Enemies the target faces in battle have a +3 to hit and add +3 to their damage when facing the target.

It should be known that the target does not have to be human, or even a person. It can be a city (in which case the lock of hair would be a brick or map of the city), a lineage, or even a religion. In this case, sacred temples of a religion, if the 4th effect is rolled, would be infested with spiders and other insects. If the target is a city and 6 is rolled, then enemies attacking the city will appear stronger than normal and more violent too.

After 1 week has passed, a new, more powerful cursed effect begins. Roll 1d10 on the table below. For every additional month, roll another 1d10. If the same effect is rolled, it increases in potency OR you cross out the old effect and create a new one.

1. The target is haunted by a variety of specters, wraiths, banshees, and other undead. They appear every night at midnight to assail the target.
2. Everything the target is touched by or touches is turned into a precious gem or metal of your choice.
3. Anything that looks at the target or that the target locks eyes with is petrified.
4. Any water that comes into contact with the target turns into blood.
5. Someone close to the target dies a sudden, horrible, ghastly death. If rerolled, another person dies.
6. A powerful, otherworldly force becomes aware of the target's existence and wishes to either end it or enslave it.
7. The target vomits up vermin such as spiders, snakes, and rats every night at midnight. These vermin are hostile towards the target once spawned.
8. The target's health begins to plummet wildly. They lose point in their Strength, Dexterity, or Constitution scores per day. If any are reduced to 0, they die.
9. The target becomes obsessed with some insane goal or nonsensical plan. If a place or religion, anything that considers it a high priest or official is instead obsessed with some insane goal or nonsensical plan.
10. Everything the target owns begins to rot away. Food molds, armor rusts or spoils, weapons break, etc.

Curses can only be broken through esoteric and strange ways. Each way is different, and the caster knows how the curse can be broken the moment it is cast. See Frostbitten & Mutilated for a bunch of ways to break a curse. I'll make my own up later.

If you fail the casting of this spell, roll 1d6 on the mishandling table below.

1. You are instantly afflicted by the spell.
2. You are instantly afflicted by one of the more potent d10 effects of the spell.
3. The spell curses the person you most love in this world. This can be a place or religion as well.
4. The spell calls forth the attention of an angel, who seeks to smite or enslave you for casting such a wicked thing.
5. Your hate spirals out of control. You become obsessed with your target and will only take actions to destroy them.
6. Your target knows your location, that you attempted to curse them, and how to most easily kill you. They are also given an emotional drive to do so.