I’d choose magic rules based on when you want players to make hard choices: before casting, while casting, or when spending resources. Start with the resource system, then decide whether casting itself needs a roll.
- Strict Vancian magic: Prepare each spell use ahead of time. Planning matters, but an unexpected problem can leave you without the right spell.
- Flexible slots: Choose from eligible spells during play. Track your spell list and remaining slots, rather than separate prepared copies.
- Casting rolls: Add a chance that a spell won’t activate. These can work with slots or mana; agree on failure costs first.
- Mana: Pay for spells from one point pool. You get more spending freedom, but spell costs and recovery rates shape your limits.
Quick Comparison
| System | What limits casting? | Does activation need a roll? | What do you track? |
|---|---|---|---|
| Strict Vancian | Prepared spell uses | Usually no | Each prepared copy |
| Flexible slots | Slots and eligible spells | Usually no | Spell list and slots by level |
| Casting rolls | Roll results plus resource rules | Yes | Checks, costs, and failure effects |
| Mana | Points and spell costs | Usually no | Point balance, costs, and recovery |
Automatic activation doesn’t mean automatic success against a target. Attacks can still miss, and targets can pass saves. A separate casting check adds another hurdle: on a d20, DC 15 with a +5 bonus gives a 55% activation chance.
My advice: test your choice for one short session before committing. Include repeated casting, an unexpected obstacle, and a low-resource finish. Then compare decision time, tracking, and player frustration.
Vancian Magic vs. Spell Slots vs. Mana: Choose Your Rules
Why I’m Ditching Spell Slots for Good
Vancian Preparation vs. Flexible Spell Slots
Spell slots don’t work the same way in every system. Some use up prepared copies of spells. Others let you spend a slot to cast any eligible spell from your prepared list. The difference is how much you can decide during play.
| Consideration | Strict Vancian preparation | Flexible spell slots |
|---|---|---|
| Planning pressure | Predict which spells you’ll need and how many times you’ll cast each. | Prepare a useful spell list, then choose how often to cast each during play. |
| Repeat-casting | Prepare a separate copy for every casting. | Cast a prepared spell again while suitable slots remain. |
| Unexpected needs | Knowing the right spell won’t help if you didn’t prepare it. | Cast any prepared spell that fits an available slot. |
| Tracking | Mark off each prepared copy as you use it. | Track your prepared list and remaining slots by level. |
Vancian Magic Uses Up Each Prepared Spell
You prepare every casting in advance, then use up that copy when you cast it. Preparing extra copies lets you repeat a spell, but leaves less room for other spells.
For example, with four first-level preparation spaces, you might prepare magic missile twice, shield once, and detect magic once. Casting magic missile uses up one copy; casting it again uses the second copy. Unused detect magic does not create another magic missile.
Give each prepared use its own checkbox so you can see what’s left. The trade-off? A missed prediction can leave you without the spell you need, even if you know it. This model rewards scouting and advance information, not just guessing what the GM has planned.
Flexible Slots Let You Choose Spells During Play
For example, if a wizard has shield, misty step, and fireball prepared, with two first-level slots and one third-level slot remaining, casting shield spends one first-level slot without removing shield from the list. Another shield can use the remaining first-level slot; fireball needs the third-level slot. Those first-level slots can’t cast misty step or fireball.
Track your prepared spells separately from your remaining slots by level. Preparation limits and spell levels still apply, and recovery rules determine when slots return. You have fewer individual copies to track, but you still need to budget your casting resources.
Once slots are in play, the next question is whether casting itself can still fail.
Casting Rolls: Add a Chance of Failure
Slots determine what you can cast. Casting rolls determine whether the spell activates.
Attack rolls and saving throws come after activation and resolve the spell’s effect. You can add casting rolls to any resource model. They add uncertainty, not access to more spells.
| Consideration | Casting roll | No activation check |
|---|---|---|
| Success chance | DC 15 with +5 succeeds on 10 or higher: 55% before situational modifiers. | Activation is automatic when requirements are met, unless another rule prevents it. |
| Failure consequence | May waste resources, cause fatigue, or trigger a mishap. | Attacks can still miss, and targets can resist. |
| Risk | The spell may not activate. | Risk comes from resource limits, defenses, positioning, and timing. |
| Speed | Adds a check and possible consequences. | Skips the check; attacks or saves may follow. |
Before using casting rolls, decide when players pay the cost and what happens on a failure.
Determine Success, Failure, and Resource Costs
Set payment timing before play: pay before rolling, pay only on success, or pay on every attempt. Then define what failure means: no effect, lost resources, fatigue, a complication, or a mishap. Players should know the cost before they roll, not discover it after a failure.
For example, under a pay on every attempt rule, casting fireball spends one 3rd-level slot and requires a casting ability check against DC 15. A total of 17 activates the spell; creatures then make saving throws. A total of 12 fails with no blast. Mark off the slot either way.
Weigh Magical Risk Against Extra Rolls
Casting rolls suit groups that want uncertain magic and risks that matter. They don’t give players more casting freedom: preparation, known spells, slots, or mana still determine what they can attempt. Choose automatic activation if your group prefers dependable abilities and fast resolution.
Unlimited retries can make failure feel like extra dice rolling rather than a setback. To keep failure meaningful, limit retries. You might forbid another attempt until the situation changes, or require checks only in dangerous conditions.
Mana Pools: Pay for Spells With Points
Spell slots limit access; mana limits spending. A mana pool is a point budget: each spell you have access to costs points from that pool. Mana doesn’t remove casting time, components, range, or other spell limits. It controls what you can spend, not whether a spell succeeds.
Budget Mana Across Different Spells
A mana pool lets players decide how to spend their power in the moment.
Using sample costs for illustration only, start with 20 mana: magic missile costs 2, invisibility costs 5, and fireball costs 8. One fireball leaves 12 mana - enough for six magic missiles, two invisibility spells with 2 points left, or one invisibility and three magic missiles with 1 point left.
That shared budget lets you cast a favorite spell repeatedly without preparing extra copies. Before play, agree on whether repeat casts have cooldowns or per-scene limits.
Compare Spending Freedom, Tracking, and Recovery
One pool replaces per-spell counters, but you’ll still track different spell costs and regeneration. Temporary bonuses add more math. Keep spell prices beside their descriptions and use a visible counter.
Recovery rate matters as much as cost. Set recovery timing and amounts before choosing the pool size, based on how many encounters you expect. Full recovery after a long rest makes mana a day-long budget. Frequent recovery encourages players to spend now. If large pools and fast recovery make mana too plentiful, slow recovery or add per-scene limits.
Conclusion: Choose the Magic Rules That Fit Your Group
Pick the magic system your group will enjoy. Strict Vancian rewards planning ahead, flexible slots let players choose in the moment, casting rolls add risk, and mana makes magic a budget to manage.
Use those trade-offs to guide your group’s choice.
Identify Your Priorities With 4 Questions
Ask the group to rank these four priorities:
- How much should planning ahead matter? Choose strict preparation.
- How much freedom should players have when choosing spells in the moment? Choose flexible slots.
- Should casting involve risk? Choose casting rolls.
- Should players budget their power? Choose mana.
Agree on the experience you want, then use the game’s own rules summary to find the rules that fit.
Test Combined Rules Before Committing
If two options still feel close, test the smallest combined rule set first. Give each mechanic a separate job: mana can handle depletion, while casting rolls handle risk.
Run one short session that includes repeated casting, an unexpected obstacle, and a low-resource finale. Track decision time, rules overhead, and frustration. Afterward, adjust one variable at a time.
